Epitaxial growth of InN films on lattice-matched EuN buffer layers

Indium nitride (InN) films have been grown on lattice matched europium nitride (EuN) buffer layers by pulsed laser deposition (PLD) and their structural properties have been investigated. It has been revealed that the growth of EuN films on Al₂O₃ (0 0 0 1) substrates leads to the formation of polycrystalline EuN films, whereas epitaxial EuN (1 1 1) films grow on MgO (1 1 1) substrates at 860 °C. By using the EuN (1 1 1) films as buffer layers for InN growth, we have succeeded in the epitaxial growth of InN (0 0 0 1) films at 490 °C with an in-plane epitaxial relationship of [1 1 2¯ 0]_InN∥[1 1¯ 0]_EuN∥[1 1¯ 0]_MgO, which minimized the lattice mismatch between InN and EuN.     

Growth of cubic InN films with high phase purity by pulsed laser deposition

Cubic InN films have been grown on MgO (1 0 0) substrates with cubic GaN buffer layers by pulsed laser deposition (PLD). It has been found that cubic InN (1 0 0) films grow on the GaN (1 0 0)/MgO (1 0 0) structure with an in-plane epitaxial relationship of [0 0 1]_InN∥[0 0 1]_GaN∥[0 0 1]MgO. The phase purity of a cubic InN film grown at 440 °C was as high as 99% that can probably be attributed to the enhanced surface migration of film precursors in case of PLD. These results indicate that PLD is a suitable technique for the growth of high-quality cubic InN films, and will makes it possible to fabricate optical and electron devices based on cubic InN films.     

Spatially incoherent Fourier digital holography by four-step phase-shifting rotational shearing interferometer and its image quality

Spatially incoherent Fourier digital holography using a rotational shearing interferometer for four-step phase-shifting method is proposed. The previous incoherent Fourier holography using a rotational shearing interferometer [Watanabe and Nomura (Appl. Opt. 54:A18, 2015)] employs the two-step phase-shifting method in the vertical and horizontal polarizations. The reconstructed image contains a large bias term. This paper proposes introduction of two kinds of wave plates in one path of a rotational shearing interferometer for a four-step phase-shifting method. A Fourier hologram is obtained from the four recorded holograms for eliminating the bias term and the twin image. The numerical simulation and the optical experiment demonstrate improvement of the image quality of reconstructed image by the twin image and bias level reduction. Furthermore, the effect of the size of an image sensor on the image quality in rotational shearing interferometer is also investigated by the numerical simulations.     

The 4d-4f dipole resonance of the Pr atom in an endohedral metallofullerene, Pr@C82

The photoion yield spectra of an endohedral metallofullerene Pr@C₈₂ were measured in the photon energy range of 100-150 eV by using time-of-flight mass spectrometry. Parent ions Pr@C₈₂⁺, Pr@C₈₂²⁺ and Pr@C₈₂³⁺ were observed in the mass spectra. The photoion yield spectra of Pr@C₈₂²⁺ showed a broad peak at 120-140 eV that was assigned to the 4d-4f giant dipole resonance of the encapsulated Pr atoms. Absolute photoabsorption cross sections of Pr@C₈₂ were evaluated from the photoion yield spectra to be 37±12 Mb at 110 eV (off-resonance) and 52±13 Mb at 130 eV (on-resonance). These cross sections of Pr@C₈₂ were compared with the results of Ce@C₈₂, the only metallofullerene whose photoionization properties have ever been studied near the 4d edge of the encapsulated metal atom. The enhancement of photoabsorption due to the giant resonance was found to be similar in Pr@C₈₂ and Ce@C₈₂, but there are marked differences in the peak shapes, which can be explained as due to interference effects between the fullerene cage and the encapsulated metal atoms.     

Intrauterine devices and uterine peristalsis: evaluation with MRI

Intrauterine devices (IUDs) have been viewed as an effective form of contraception. However, the mechanism by which IUDs disturb fertility remains controversial. This study aimed to evaluate the effects of IUDs on uterine contractility using cine MR. Eleven healthy female volunteers of reproductive age bearing IUDs and 12 women not bearing IUDs were evaluated during the periovulatory phase. MR images were obtained with a 1.5-T magnet, acquiring 60 serial images every 3 s via half-Fourier acquisition single-shot turbo spin echo to be displayed on cine mode. Assessments were based on (a) the presence of peristaltic waves, (b) the frequency and direction of peristaltic waves and (c) the extent of peristaltic waves. Static images were evaluated for thickness of the junctional zone (JZ) and myometrium. A fundo-cervical (FC)-directed peristaltic wave was identified in 4 of 11 IUD-bearing subjects and in only 1 of 12 subjects from the control group. FC waves extended through more than half of the thickness of the myometrium. Peristaltic frequency in IUD users (5.0/3 min) was less than that of the control group (6.5/3 min). The JZ and myometrium were significantly thicker in IUD users. FC-directed waves were more often observed in IUD-bearing subjects, which might explain the inhibition of active sperm transport.     

Mapping of the cationic starch adsorbed on pulp fibers by ToF-SIMS

Cationic starch (CS) is routinely used in the papermaking process to improve the dry strength or printability of paper. The effectiveness depends on the distribution of the starch on the pulp fiber, and in this study, time-of-flight secondary ion mass spectrometry was used to investigate this distribution. The characteristic peak at 58m/z was applied to map the CS. Based on the imaging analysis of the handsheets with the CS as an internal additive, the distribution of CS became more uniform with decreasing freeness. The amount of adsorbed CS increased with increasing fiber length and was lower on vessels than on other fibers. These results were related to fibrillation. From the analysis of handsheets with CS as an external additive, the penetration depth of the starch into base paper increased with decreases in the sizing degree of the base paper.     

Experimental constraints on the phase diagram of titanium metal

The phase transformations of titanium metal have been studied at temperatures and pressures up to 973 K and 8.7 GPa using synchrotron X-ray diffraction. The equilibrium phase boundary of the α-ω transition has a dT/dP slope of 345 K/GPa, and the transition pressure at room temperature is located at 5.7 GPa. The volume change across the α-ω transition is ΔV=0.197 cm³/mol, and the associated entropy change is ΔS=0.57 J/mol K. Except for ΔV, our results differ substantially from those of previous studies based on an equilibrium transition pressure of 2.0 GPa at room temperature. The α-ω-β triple point is estimated to be at 7.5 GPa and 913 K, which is comparable with previous results obtained from differential thermal analysis and resistometric measurements. An update, more accurate phase diagram is established for Ti metal based on the present observations and previous constraints on the α-β and ω-β phase boundaries.     

Hydrogen desorption processes in Li-Mg-N-H systems

Li-Mg-N-H systems composed of Mg(NH₂)₂ and LiH with various ratios can reversibly store a large amount of hydrogen under the temperature condition above 150 °C. These composites with 3:6, 3:8 and 3:12 ratio of Mg(NH₂)₂ and LiH have been independently reported by four groups as promising candidates of high performance hydrogen storage materials possessing the reversibility and the high capacity. In any cases, an interaction between NH₃ and LiH plays an important role for the progress of hydrogen desorbing and absorbing reactions. For the hydrogen desorption process, the NH₃ molecule generated from Mg(NH₂)₂ reacts with LiH, forming LiNH₂ and H₂. Especially, under an equilibrium condition, in situ diffraction results indicated that the single phase of LiNH₂·MgNH (LiMgN₂H₃) could be generated other than the separated two phases. As a next step, the NH₃ molecule generated from LiNH₂ reacts with LiH, desorbing H₂. As a result, the dehydrogenated phase was evaluated to be Li₂NH·MgNH (Li₂MgN₂H₂) or separated two phases, in which the final phase should depend on the experimental conditions. Thus, if the amount of LiH is enough to react with NH₃, the hydrogen desorption processes are described by the NH₃ generation from the corresponding amides and the imide.