Optical excitation of optically inactive photonic band modes

At the point Γ of the Brillouin zone of photonic crystals (PCs), there are many photonic band (PB) states that do not couple to the incoming plane wave beams. This paper investigates how to excite these optically inactive PB (OIPB) modes in slab PCs by using optical means. Three methods are proposed, using a prism, traveling charges and focused laser pulses, each making use of evanescent light to excite OIPBs. It is concluded that to accumulate photons in an OIPB, sequential passing of bunched charges or intermittent irradiation of focused laser pulses is effective. The effect of the lateral size of the practical PC slabs is also discussed and it is found that the conclusions for an ideal system of infinite size still work if the lateral size is order of magnitudes larger than the PC lattice constant.     

Phase Relations and EOS of ZrO 2 and HfO 2 Under High-temperature and High-pressure

The phase relations and equations of state of ZrO 2 and HfO 2 high-pressure polymorphs have been investigated by means of in situ observation using multi-anvil type high-pressure devices and synchrotron radiation. Baddeleyite (monoclinic ZrO 2 ) transforms to two distorted fluorite (CaF 2 )-type phases at 3-4 GPa depending on temperature: an orthorhombic phase, orthoI, below 600 °C and a tetragonal phase, which is one of the high-temperature forms of ZrO 2 , above 600 °C. Both orthoI and tetragonal phases then transform into another orthorhombic phase, orthoII, with a cotunnite (PbCl 2 )-type structure above 12.5 GPa and the phase boundary is almost independent of temperature. OrthoII is stable up to 1800 °C and 24 GPa. In case of HfO 2 , orthoI is stable from 4 to 14.5 GPa below 1250-1400 °C and transforms to the tetragonal phase above these temperatures. OrthoII of HfO 2 appears above 14.5 GPa and is stable up to 1800 °C at 21 GPa. The unit cell parameters and the volumes of these high-pressure phases have been determined as functions of pressure and temperature. The orthoI/tetragonal-to-orthoII transition of both ZrO 2 and HfO 2 is accompanied by about 9% volume decrease. The bulk moduli of orthoII calculated using Birch-Murnaghan's equations of state are 296 GPa and 312 GPa for ZrO 2 and HfO 2 , respectively. Since orthoII of both ZrO 2 and HfO 2 are quenchable to ambient conditions, these are candidates for super-hard materials.     

A new high‐pressure strontium germanate,SrGe2O5

The Sr–Ge–O system has an earth‐scientific importance as a potentially good low‐pressure analog of the Ca–Si–O system, one of the major components in the constituent minerals of the Earth's crust and mantle. However, it is one of the germanate systems that has not yet been fully examined in the phase relations and structural properties. The recent findings that the SrGeO₃ high‐pressure perovskite phase is the first Ge‐based transparent electronic conductor make the Sr–Ge–O system interesting in the field of materials science. In the present study, we have revealed the existence of a new high‐pressure strontium germanate, SrGe₂O₅. Single crystals of this compound crystallized as a co‐existent phase with SrGeO₃ perovskite single crystals in the sample recovered in the compression experiment of SrGeO₃ pseudowollastonite conducted at 6 GPa and 1223 K. The crystal structure consists of germanium–oxygen framework layers stacked along [001], with Sr atoms located at the 12‐coordinated cuboctahedral site; the layers are formed by the corner linkages between GeO₆ octahedra and between GeO₆ octahedra and GeO₄ tetrahedra. The present SrGe₂O₅ is thus isostructural with the high‐pressure phases of SrSi₂O₅ and BaGe₂O₅. Comparison of these three compounds leads to the conclusion that the structural responses of the GeO₆ and GeO₄ polyhedra to cation substitution at the Sr site are much less than that of the SrO₁₂ cuboctahedron to cation substitution at the Ge sites. Such a difference in the structural response is closely related to the bonding nature.     

A one-pot procedure for trifluoroacetylation of arylamines using trifluoroacetic acid as a trifluoroacetylating reagent

A convenient procedure for the preparation of aryl trifluoroacetamides from aryl amines is described that employs 2-4 M equiv of trifluoroacetic acid in refluxing xylene as a trifluoroacetylating agent. Addition of an amount of pyridine that is equimolar to the amount of trifluoroacetic acid present in the reaction mixture facilitates the trifluoroacetylation of rather basic arylamines.     

Bioisosteric transformation of H1-antihistaminic benzimidazole derivatives

With the aim of obtaining new H1-antihistaminic agents, transformations of previously reported antihistaminic benzimidazoles were performed on the basis of the concept of bioisosterism. Among the compounds prepared, imidazo[4,5-b]pyridine (8) and 4(3H)-quinazolinone (11) exhibited significant H1-antihistaminic activity.     

Potential nootropic agents, 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives

A series of 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives was synthesized and evaluated for its ability to reverse a scopolamine-induced learned impairment in a one-trial passive avoidance task (antiamnestic activity). 2-(4-Allyl-1-piperazinyl)-4-pentyloxyquinazoline (4) showed more potent antiamnestic activity than such reference compounds as aniracetam, idebenone and bifemelane at a wide dose range (1-30 mg/kg]. Compound 4 also exhibited potent anticonvulsive and antihypoxic activities, and was selected as the most promising nootropic candidate agent.     

Smith-Purcell radiation from a charge running near the surface of a photonic crystal

Smith-Purcell radiation from a charge running near a photonic crystal is calculated for a slab system of a periodic array of dielectric spheres, with the photonic band effect taken into account exactly. The radiation spectrum has a series of resonantly enhanced structures, which are shown to arise accompanying the excitation of the photonic bands. It is also shown that the overall intensity of the emission band does not depend very strongly on the slab thickness but the height of the resonant peaks increases progressively with thickness due to the enhanced Q value of excited photonic bands.     

Pressure-induced sharp coordination change in liquid germanate

Local structures around germanium in liquid germanate have been investigated by means of in situ x-ray absorption measurements up to 9 GPa at 1273 K. Liquid germanate consisting of tetrahedrally coordinated germanium contracts with increasing pressure without significant changes in the local structure up to 2.5 GPa and then shows an abrupt fourfold-to-sixfold coordination change around 3 GPa. The coordination change is completed below 4 GPa where upon a high-density liquid consisting of octahedrally coordinated germanium becomes stable. The GeO6 octahedron in the high-density liquid is more compressible than that in solids.     

Photo-and-thiol-driven trans insertion of phenylacetylene into H-Pt bonds

The photo-and-thiol-driven trans insertion of phenylacetylene into H-Pt bonds of Pt(X)(H)(PPh3)2 (X = SAr, Cl, Br, and I) took place to afford Pt[(Z)-C(H)=CH(Ph)](X)(PPh3)2 in good yields.