Phase equilibrium temperature and dissociation enthalpy in the tri-n-butylalkylphosphonium bromide semiclathrate hydrate systems

Semiclathrate hydrate (SCH) is one of the phase change materials suitable for cold storage. The thermodynamic properties of SCHs, such as an equilibrium temperature and a dissociation enthalpy, depend on the size and shape of guest substances. In this study, to reveal the effect of cation size and shape on the thermodynamic properties, tri-n-butylalkylphosphonium bromide (P444R-Br) SCHs, where the alkyl group was n-propyl (R = 3), n-butyl (R = 4), n-pentyl (R = 5), i-butyl (R = i-4), i-pentyl (R = i-5), or allyl (R = Al)), were investigated. The branched alkyl groups (R = i-4 or i-5) raised the equilibrium temperature, whereas the shorter alkyl groups (R = 3 or Al) lowered one. Except for P4445-Br and P444(Al)-Br SCHs, the other P444R-Br SCHs had the same orthorhombic structure. Among the orthorhombic systems in the present study, the semiclathrate hydrate with a higher equilibrium temperature had a larger dissociation enthalpy

Enhanced operation frequencies of bipolar double-flux-quantum amplifiers fabricated using 10 kA cm−2 Nb/AlOx/Nb integration process

We have demonstrated digital-to-analog (D/A) operations using single-flux-quantum (SFQ) pulse-frequency modulation (PFM) D/A converters for future AC voltage standards. In this paper, for the improvement of SFQ-PFM D/A converters, we investigated a double-flux-quantum amplifier (DFQA) and a magnetically-coupling SFQ driver/receiver circuit (MC-SFQ-DR) fabricated using a 10 kA cm−2 Nb/AlOx/Nb integration process. The critical current density Jc of 10 kA cm−2 was four times larger than that of the integration process we had used. A DFQA and an MC-SFQ-DR included unshunted Josephson junctions, and therefore, it was unclear if the high-Jc process improved their performances. We measured test chips cooled in a liquid helium bath. The maximum input voltages for a +20 fold and a −20 fold DFQA were 147 and 126 μV, for which the corresponding Josephson frequencies were 70.9 and 61.1 GHz. It was confirmed that the operation frequencies of the DFQAs and MC-SFQ-DR were improved approximately two-fold

Scaling the stimulated emission of polarization-entangled photons using passive optical components

Bright sources of polarization-entangled photon pairs are essential components for quantum information technologies. In general, it is necessary to introduce a resonator that combines active optical components such as an electric optical modulator to enhance the stimulated emission of polarization-entangled photons. It is technically difficult to perform the time series operation to output the stimulated entangled photons in the resonator by synchronizing laser pulses. In this paper, we propose a scheme to scale up the stimulated emission of polarization-entangled photon pairs using a resonator with only passive optical components. We show the theoretical aspects of the scheme and also perform a proof-of-principle experimental demonstration of the scheme in a double-pass configuration.Comment: 8 pages, 6 figures, Physical Review A to be publishe

Direction of collaborative problem solving-based STEM learning by learning analytics approach.

The purpose of this study was to explore the factors that might affect learning performance and collaborative problem solving (CPS) awareness in science, technology, engineering, and mathematics (STEM) education. We collected and analyzed data on important factors in STEM education, including learning strategy and learning behaviors, and examined their interrelationships with learning performance and CPS awareness, respectively. Multiple data sources, including learning tests, questionnaire feedback, and learning logs, were collected and examined following a learning analytics approach. Significant positive correlations were found for the learning behavior of using markers with learning performance and CPS awareness in group discussion, while significant negative correlations were found for some factors of STEM learning strategy and learning behaviors in pre-learning with some factors of CPS awareness. The results imply the importance of an efficient approach to using learning strategies and functional tools in STEM education

Reduction of T-Box 15 gene expression in tumor tissue is a prognostic biomarker for patients with hepatocellular carcinoma

Genome-wide analysis is widely applied to detect molecular alterations during oncogenesis and tumor progression. We analyzed DNA methylation profiles of hepatocellular carcinoma (HCC), and investigated the clinical role of most heypermethylated of tumor, encodes T-box 15 (TBX15), which was originally involved in mesodermal differentiation. We conducted a genome-wide analysis of DNA methylation of tumor and non-tumor tissue of 15 patients with HCC, and revealed TBX15 was the most hypermethylated gene of tumor (Beta-value in tumor tissue = 0.52 compared with non-tumor tissue). Another validation set, which comprised 58 HCC with radical resection, was analyzed to investigate the relationships between tumor phenotype and TBX15 mRNA expression. TBX15 mRNA levels in tumor tissues were significantly lower compared with those of nontumor tissues (p < 0.0001). When we assigned a cutoff value = 0.5-fold, the overall survival 5-year survival rates of the low-expression group (n = 17) were significantly shorter compared with those of the high-expression group (n = 41) (43.3% vs. 86.2%, p = 0.001). Multivariate analysis identified low TBX15 expression as an independent prognostic factor for overall and disease-free survival. Therefore, genome-wide DNA methylation profiling indicates that hypermethylation and reduced expression of TBX15 in tumor tissue represents a potential biomarker for predicting poor survival of patients with HCC