The impact of an intermediate temperature buffer on the growth of GaN on an AlN template by hydride vapor phase epitaxy

The present study focused on the effect of an intermediate-temperature (IT; ∼900 °C) buffer layer on GaN films, grown on an AlN/sapphire template by hydride vapor phase epitaxy (HVPE). In this paper, the surface morphology, structural quality, residual strain, and luminescence properties are discussed in terms of the effect of the buffer layer. The GaN film with an IT-buffer revealed a relatively lower screw-dislocation density (3.29×10⁷ cm⁻²) and a higher edge-dislocation density (8.157×10⁹ cm⁻²) than the GaN film without an IT-buffer. Moreover, the IT-buffer reduced the residual strain and improved the luminescence. We found that the IT-buffer played an important role in the reduction of residual strain and screw-dislocation density in the overgrown layer through the generation of edge-type dislocations and the spontaneous treatment of the threading dislocation by interrupting the growth and increasing the temperature.     

Comprehensive Understanding of Structure‐Controlling Factors of a Zinc Tetraphenylporphyrin Thin Film Using pMAIRS and GIXD Techniques

The performance of an organic electronic device is significantly influenced by the anisotropic molecular structure in the film, which has long been difficult to predict especially for a solution process. In the present study, a zinc tetraphenylporphyrin (ZnTPP) thin film prepared by a solution process was chosen to comprehensively explore the molecular‐arrangement mechanism as a function of representative film‐preparation parameters: solvent, film‐preparation technique, and thermal annealing. The anisotropic structure was first analyzed by using a combination of infrared p‐polarized multiple‐angle incidence resolution spectrometry (pMAIRS) and grazing incidence X‐ray diffraction (GIXD), which readily revealed the molecular orientation and crystal structure, respectively. As a result, the real dominant factor was found to be the evaporation time of the solvent that determines the initial two different molecular arrangements, types‐I and ‐II, while the thermal annealing was found to play an additional role of improving the molecular order. The correlation between the molecular orientation and the crystal structure was also revealed through the individual orientation analysis of the porphyrin and phenyl rings.     

Majorana neutrinos as the dark matters in the cold plus hot dark matter model

A simple model of the Majorana neutrino with the see-saw mechanism is studied, assuming that two light neutrinos are the hot dark matter each with a mass of 2.4 eV in the cold plus hot dark matter model of cosmology. We find that the heavy neutrino, which is the see-saw partner with the remaining one light neutrino, can be the cold dark matter, if the light neutrino is exactly massless. This cold dark matter neutrino is allowed to have a mass in the wide range from 5.9 × 10² eV to 2.2 × 10⁷ eV.     

NMR relaxation of 7Li in concentrated lithium-ammonia solutions

The Knight shift and the spin-lattice relaxation time of ⁷Li in lithium-ammonia solutions have been measured at -57°C over the concentration range X_Li = 0.01–0.20 (X_Li: mole fraction of Li). The Knight shift increases with increasing metal concentration, while the relaxation rate, 1/T₁, shows a broad minimum around X_Li = 0.07.     

Dual modification of a triple-stranded β-helix nanotube with Ru and Re metal complexes to promote photocatalytic reduction of CO2

We have constructed a robust β-helical nanotube from the component proteins of bacteriophage T4 and modified this nanotube with Ru(II)(bpy)(3) and Re(I)(bpy)(CO)(3)Cl complexes. The photocatalytic system arranged on the tube catalyzes the reduction of CO(2) with higher reactivity than that of the mixture of the monomeric forms.     

NMR study of YP and YPO4 as 2-qubits quantum computers

The ³¹P-NMR experiments in YP and YPO₄ as 2-qubits quantum computers were performed at room temperature under magnetic fields of 6.3 and 11.75 T with a coherent type pulsed FT-NMR spectrometer. The full width at half of the maximum intensity of NMR spectrum for ³¹P is compared with the second moment caused by the dipolar field. The obtained spin–lattice relaxation times T₁ of 1.2 and 320 s for the P nuclei in YP and YPO₄, respectively, suggest both compounds have the advantage of increasing the numbers of quantum computing operations.     

Intramolecular Aminolactonization for Synthesis of Furoindolin-2-One

Propellanes are polycyclic compounds in which tricyclic systems share one carbon–carbon single bond. Propellane frameworks that consist of larger sized rings are found in a variety of natural products. As an approach to the stereoselective synthesis of the propellane framework, one of the efficient methods is forming several rings in a single operation. Lapidilectine B (1) is composed of a propellane framework and was synthesized through the oxidative cyclization of trisubstituted alkenes. When the alkene with an ester moiety was treated with N-iodosuccinimide (NIS), iodocyclization proceeded to give the cyclic carbamate. On the other hand, when PhI(OAc)₂ was allowed to react in the carboxyl form, a furoindolin-2-one structure corresponding to the A-B-C ring of lapidilectine B (1) was produced. Furthermore, when Pd(OAc)₂ catalyst was used for cyclization under oxidative conditions, the product yield was improved.     

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitors V. A series of new derivatives containing a spiro[imidazo[1,2-a]pyrazine-2(3H),4'-piperidin]-5(1H)-one scaffold

We have already reported unique compounds containing a N,O-spiro acetal structure as an orally active factor Xa (FXa) inhibitor. This time, we described a N,N-spiro acetal structure as an analogue of the N,O-spiro acetal structure for an orally active FXa inhibitor. The synthesis of these analogues could be achieved in a similar fashion to the N,O-spiro acetal synthesis. Consequently, FXa inhibitory activity was increased and more active compounds could be found (M58163: IC50 = 0.61 nM, M58169: IC50 = 0.58 nM). Additionally, the absolute configuration could be determined by X-ray crystallography analysis (M58169: (R)-config.).     

A Tray‐Shaped,PdII‐Clipped Au3 Complex as a Scaffold for the Modular Assembly of [3×n] Au Ion Clusters

A tray‐shaped Pd^II₃Au^I₃ complex ( 1 ) is prepared from 3,5‐bis(3‐pyridyl)pyrazole by means of tricyclization with Au^I followed by Pd^II clipping. Tray 1 is an efficient scaffold for the modular assembly of [3×n] Au^I clusters. Treatment of 1 with the Au^I₃ tricyclic guest 2 in H₂O/CH₃CN (7:3) or H₂O results in the selective formation of a [3×2] cluster ( 1 ? 2 ) or a [3×3] cluster ( 1 ? 2 ? 1 ), respectively. Upon subsequent addition of Ag^I ions, these complexes are converted to an unprecedented Au₃–Au₃–Ag–Au₃–Au₃ metal ion cluster.