Antioxidative copper sinter bonding under thermal aging utilizing reduction of cuprous oxide nanoparticles by polyethylene glycol

Durability of sintered Cu joints under thermal aging in the air was investigated for the reduction of Cu₂O using Cu₂O/polyethylene glycol (PEG) mixture. Thermal analysis of the Cu₂O/PEG paste showed that the molecular weight of PEG influences the redox reaction and the subsequent bonding related to the combustion of the reducing organic solvent. Sintered Cu joints using PEG 400 exhibited high joint strength (above 30 MPa) in shear tests, even for the bonding temperature of 280 °C. The sintered Cu joints exhibited slightly increased strength during thermal aging at 250 °C in air, which was also confirmed by the microscale tensile test used for evaluating the fracture behavior of the sintered Cu structure. Microstructural analysis, including the evaluation of the crystal orientation, revealed a small change in the microstructure of sintered joints during aging. Transmission electron microscopy revealed the presence of organic membranes on slightly oxidized sintered Cu grains before thermal aging, and additional oxidation was observed after thermal aging. The progress of sintering during thermal aging in vacuum was different than that in air. It was considered that the formation of a thin Cu₂O layer, controlled by the presence of organic membranes, contributed to the suppression of Cu sintering.The version of record of this article, first published in Journal of Materials Science, is available online at Publisher’s website: https://doi.org/10.1007/s10853-023-08976-

Raman study on the interlayer interactions and the band structure of bilayer graphene synthesized by alcohol chemical vapor deposition

We investigated the electronic band structure and interlayer interactions in graphene synthesized by alcohol-chemical vapor deposition (a-CVD) using microprobe Raman spectroscopy and tight-binding band-structure calculations. The number of graphene layers was determined from the spectrally integrated intensity ratios of the G phonon to 2D phonon peaks. We found that the value of the parameter determining interlayer interactions in a-CVD bilayer graphene was less than half that of exfoliated bilayer graphene. The weak interlayer interaction in a-CVD bilayer graphene was attributed to non-AB stacking order

Lyα view around a z = 2.84 hyperluminous QSO at a node of the cosmic web

We report on the results of deep and wide-field (1.1 deg²) narrow-band observations with Subaru/Hyper Suprime-Cam (HSC) of a field around a hyperluminous QSO (HLQSO), HS1549+1549+1919, residing in a protocluster at z = 2.84, to map the large-scale structure of Lyα emitters (LAEs). One HSC pointing enables us to detect 3490 LAEs and 76 extended Lyα blobs (LABs), probing diverse environments from voids to protoclusters. The HLQSO is found to be near the center of the protocluster, which corresponds to the intersection of ∼100 comoving Mpc-scale structures of LAEs. LABs are basically distributed along the large-scale structure, with larger ones particularly clustering around the HLQSO, confirming a previously noted tendency of LABs to prefer denser environments. Moreover, the shapes of LABs near the HLQSO appear to be aligned with the large-scale structure. Finally, a deep Lyα image reveals a diffuse Lyα nebula along a filamentary structure with no luminous UV/sub-mm counterpart. We suggest that the diffuse nebula is due to a cold filament with high clumping factor illuminated by the QSO, with the required high clumpiness provided by unresolved residing halos of mass ≤10⁹⁻¹⁰ M_⊙⁠

Isolation of TBP-interacting protein (TIP) from a hyperthermophilic archaeon that inhibits the binding of TBP to TATA-DNA

AbstractWe have isolated TBP (TATA-binding protein)-interacting protein (TIP) from cell lysates of a hyperthermophilic archaeon, Pyrococcus kodakaraensis KOD1, by affinity chromatography with TBP-agarose. Based on the internal amino acid sequence information, PCR primers were synthesized and used to amplify the gene encoding this protein (Pk-TIP). Determination of the nucleotide sequence and characterization of the recombinant protein revealed that Pk-TIP is composed of 224 amino acid residues (molecular weight of 25 558) and exists in a dimeric form. BIAcore analyses for the interaction between recombinant Pk-TIP and recombinant Pk-TBP indicated that they interact with each other with an equilibrium dissociation constant, KD, of 1.24–1.46 μM. A gel mobility shift assay indicated that Pk-TIP inhibited the interaction between Pk-TBP and a TATA-DNA. Pk-TIP may be one of the archaeal factors which negatively regulate transcription

A Keck/DEIMOS Spectroscopy of Lyman Alpha Blobs at Redshift z=3.1

We present the results of an intermediate resolution (~2 angstrom) spectroscopy of a sample of 37 candidate Lyman alpha blobs and emitters at redshift z=3.1 using the DEIMOS spectrograph on the 10 m Keck telescope. The emission lines are detected for all the 37 objects and have variety in their line profiles. The Lyman alpha velocity widths (FWHM) of the 28 objects with higher quality spectra, measured by fitting a single Gaussian profile, are in the range of 150 - 1700 km/s and correlate with the Lyman alpha spatial extents. All the 12 Lyman alpha blobs (>16 arcsec^2) have large velocity widths of > 500 km/s. While there are several possible physical interpretations of the Lyman alpha velocity widths (motion of gravitationally-bound gas clouds, inflows, merging of clumps, or outflows from superwinds), the large velocity widths of the Lyman alpha blobs suggest that they are the sites of massive galaxy formation. If we assume gravitationally-bound gas clouds, the dynamical masses of the Lyman alpha blobs are estimated to be ~10^12 - 10^13 Msun. Even for the case of outflows, the outflow velocities are likely to be the same order of the rotation velocities as inferred from the observational evidence for local starburst galaxies.Comment: Accepted for publication in ApJ

Data-Driven Optimal Sensor Placement for High-Dimensional System Using Annealing Machine

We propose a novel method for solving optimal sensor placement problem for high-dimensional system using an annealing machine. The sensor points are calculated as a maximum clique problem of the graph, the edge weight of which is determined by the proper orthogonal decomposition (POD) mode obtained from data based on the fact that a high-dimensional system usually has a low-dimensional representation. Since the maximum clique problem is equivalent to the independent set problem of the complement graph, the independent set problem is solved using Fujitsu Digital Annealer. As a demonstration of the proposed method, the pressure distribution induced by the K\'arm\'an vortex street behind a square cylinder is reconstructed based on the pressure data at the calculated sensor points. The pressure distribution is measured by pressure-sensitive paint (PSP) technique, which is an optical flow diagnose method. The root mean square errors (RMSEs) between the pressure measured by pressure transducer and the reconstructed pressures (calculated from the proposed method and an existing greedy method) at the same place are compared. As the result, the similar RMSE is achieved by the proposed method using approximately 1/5 number of sensor points obtained by the existing method. This method is of great importance as a novel approach for optimal sensor placement problem and a new engineering application of an annealing machine