Iron-57 mössbauer spectroscopic study of six-coordinate and seven-coordinate iron(III)-EDTA complexes

Newly prepared six-coordinate M[Fe(edta)] (M=Li, Na, K, Rb) and seven-coordinate H[Fe(edta)(H₂O)].H₂O were characterized by Mössbauer spectroscopy. The hygroscopic six-coordinate complexes were found to have high-spin Fe³⁺ ions in distorted octahedral sites.     

Quadrupole moment of41Sc by use of new nuclear quadrupole resonance detection

Quadrupole effects in -NMR spectra of⁴¹Sc(I =7/2^–,T _1/2=0.596 s) implanted in a TiO₂ single crystal were detected by use of a modified -NMR technique. Using the field gradient in the crystal determined by the pulsed-Fourier-transformed NMR of⁴⁵Sc in TiO₂, the quadrupole moment of⁴¹Sc has been determined as |Q(⁴¹Sc; 7/2^–)|=166±8 mb.     

Design Consideration for a Two-Distributed-Junction Tuning Circuit

We describe a novel method of designing a tuning circuit with two half-wave distributed junctions separated by a half-wavelength microstripline, which analytically determines the circuit parameters such as the minimum current density of the junctions and the characteristic impedances of the distributed junctions and the microstripline. The tuning circuit was approximated by simple transmission theory and then simplified with ideal circuit components for analysis. We applied Chebyshevs band-pass filter theory, in part, to optimize the circuit design. The analytical results revealed that a high characteristic-impedance ratio between the distributed junctions and the microstripline is necessary to obtain broadband matching using low-current-density junctions. The experimental results for all-NbN SIS mixers we designed with this method demonstrated double-sideband (DSB) receiver-noise temperatures of 6–10 quanta from 710 to 810 GHz for a mixer with a current density of only 4 kA/cm² (estimated C_JR_N product of 37 at 750 GHz). The RF bandwidth was broader than that of a conventional full-wave distributed SIS mixer with the same current density.     

Spherical neutron polarimetry studies on the magnetic structure of single crystal Cr1−xMoxB2 (x=0, 0.15)

By applying spherical neutron polarimetry technique to Cr_1−xMo_xB₂ (x=0, 0.15), we successfully determined its precise magnetic structures. We emphasize here that the ratio of magnetic component was determined by measuring the two satellite reflections and rotating the incident neutron spin directions.     

Aerosol generation and measurement of multi-wall carbon nanotubes

Mass production of some kinds of carbon nanotubes (CNT) is now imminent, but little is known about the risk associated with their exposure. It is important to assess the propensity of the CNT to release particles into air for its risk assessment. In this study, we conducted aerosolization of a multi-walled CNT (MWCNT) to assess several aerosol measuring instruments. A Palas RBG-1000 aerosol generator applied mechanical stress to the MWCNT by a rotating brush at feed rates ranging from 2 to 20 mm/h, which the MWCNT was fed to a two-component fluidized bed. The fluidized bed aerosol generator was used to disperse the MWCNT aerosol once more. We monitored the generated MWCNT aerosol concentrations based on number, area, and mass using a condensation particle counter and nanoparticle surface area monitor. Also we quantified carbon mass in MWCNT aerosol samples by a carbon monitor. The shape of aerosolized MWCNT fibers was observed by a scanning electron microscope (SEM). The MWCNT was well dispersed by our system. We found isolated MWCNT fibers in the aerosols by SEM and the count median lengths of MWCNT fibers were 4–6 μm. The MWCNT was quantified by the carbon monitor with a modified condition based on the NIOSH analytical manual. The MWCNT aerosol concentration (EC mass base) was 4 mg/m³ at 2 mm/h in this study.     

Cu chemistry of YBa2Cu3O6+x investigated by nuclear quadrupole resonance

The nuclear quadrupole resonance (NQR) technique has been utilized to characterize the local oxygen coordination of inequivalent Cu sites in YBa₂Cu₃O_6+x(0 ≤ x ≤ 0.91). Essentially, four distinct NQR lines which correspond to 2, 3,4 oxygen coordinated Cu sites in the Cu-O chains and 5 oxygen coordinated Cu sites in the Cu-O planes have been observed. The zero-field NQR frequencies of these are centered at about 30.1, 24.0, 22.0 and 31.5 MHz for ⁶³Cu, respectively. For the antiferromagnetic ordered state (x ≤ 0.3), antiferromagnetic nuclear resonance (AFNR) has been observed at 90 MHz with quadrupole splittings associated with the moment-bearing Cu sites in the Cu-O planes. The relative intensities of these resonance lines depend on the oxygen content, and this gives us a microscopic understanding of the Cu chemistry of this system.     

Recrystallization and formation of spheroidal gold particles in amorphous-like AlN–TiB<Subscript>2</Subscript>–TiSi<Subscript>2</Subscript> coatings after annealing and subsequent implantation

The recrystallization of the structure of an X-ray amorphous AlN–TiB₂–TiSi₂ coating containing short-range order regions with characteristic sizes of 0.8–1.0 nm has been performed using a negative gold ion (Au^–) beam and high-temperature annealing. Direct measurements using methods of high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectral (EDXS) microanalysis have demonstrated that thermal annealing at a temperature of 1300°C in air results in the formation of nanoscale (10–15 nm) phases AlN, AlB₂, Al₃O₃, and TiO₂, whereas the ion implantation of negative ions Au^– leads to a fragmentation (decrease in the size) of nanograins to 2–5 nm with the formation of spheroidal gold nanocrystallites a few nanometers in size, as well as to the formation of an amorphous oxide film in the depth (near-surface layer) of the coating due to ballistic ion mixing and collision cascades.     

Enhanced renal image contrast by ethanol fixation in phase‐contrast X‐ray computed tomography

Phase‐contrast X‐ray imaging using a crystal X‐ray interferometer can depict the fine structures of biological objects without the use of a contrast agent. To obtain higher image contrast, fixation techniques have been examined with 100% ethanol and the commonly used 10% formalin, since ethanol causes increased density differences against background due to its physical properties and greater dehydration of soft tissue. Histological comparison was also performed. A phase‐contrast X‐ray system was used, fitted with a two‐crystal X‐ray interferometer at 35 keV X‐ray energy. Fine structures, including cortex, tubules in the medulla, and the vessels of ethanol‐fixed kidney could be visualized more clearly than that of formalin‐fixed tissues. In the optical microscopic images, shrinkage of soft tissue and decreased luminal space were observed in ethanol‐fixed kidney; and this change was significantly shown in the cortex and outer stripe of the outer medulla. The ethanol fixation technique enhances image contrast by approximately 2.7–3.2 times in the cortex and the outer stripe of the outer medulla; the effect of shrinkage and the physical effect of ethanol cause an increment of approximately 78% and 22%, respectively. Thus, the ethanol‐fixation technique enables the image contrast to be enhanced in phase‐contrast X‐ray imaging.     

Role of propagating modes in a double-groove grating with a +1st-order diffraction angle larger than the substrate-air critical angle

Here we show, analytically and numerically, that in a TiO(2) double-groove grating with two different groove widths per period attached on the SiO(2) substrate, the normally incident light couples to the +1st-order transmission with 96.9% efficiency and with a 50° diffraction angle that is larger than the SiO(2)-air interface critical angle. Modal analysis reveals that three propagating modes for the +1st diffraction order reach the grating back end in phase, while the corresponding propagating modes for the -1st and zeroth orders are added destructively at the grating end. Four optical devices based on this grating characteristic are numerically demonstrated.