Structure and photoluminescence properties of a rare-earth free red-emitting Mn(2+)-activated KMgBO3.

In this combined X-ray diffraction and photoluminescence study, the coordination environment of Mn(2+) and the photoluminescence of single Mn(2+) doped KMgBO3 phosphors were studied. Mn(2+) occupies Mg(2+) sites, which were coordinated by six O(2-). The strong absorption of KMgBO3:Mn(2+) was ascribed to the strong relaxation of spin and parity forbidden d-d transitions of Mn(2+). The emission bands were centered at 636 nm, regardless of the excitation wavelength and Mn(2+) doping concentration. Mn(2+) activated KMgBO3 could be efficiently excited with the excitation of Mn(2+) d-d transitions in the wavelength range of 300-475 nm. The red-shift of Mn(2+) emission was because of the strong crystal field environment of Mn(2+) afforded by KMgBO3. The potential applications of the phosphors have been pointed out based on their absorption spectra, excitation and emission spectra, thermal quenching properties, and decay properties.

Structure determination and relative properties of novel chiral orthoborate KMgBO3.

A novel chiral orthoborate, KMgBO(3), has been successfully synthesized via a standard solid-state reaction, and the crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the cubic chiral space group P2(1)3. Isolated [BO(3)](3-) anionic groups, which are the fundamental building units, are distributed around the 111 crystallographic direction in an axial C(3) symmetry, and the configuration of O(3) planes is helical, similar to the aplanar ClO(3) groups in NaClO(3), which indicates an optical activity in it and is validated by the circular dichroism spectrum. The chiral feature of the borate is unique, and because of the noncentrosymmetric structure, the compound exhibits nonlinear optical properties, which are validated by second harmonic generation powder measurement. It has a wide transparency, including the vacuum ultraviolet region. The relations between the structures of KMgBO(3) and NaClO(3) and structural conversion form KMgBO(3) to NaMgBO(3) are also discussed. The ionic radii, interatomic distance, and the rigid tilting of BO(3) groups are considered to be the main factors in the crystallization of different structures.

Structure determination of novel orthoborate NaMgBO(3): a promising birefringent crystal.

A novel orthoborate, NaMgBO(3), has been successfully synthesized by a standard solid-state reaction, and the crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the monoclinic space group C2/c with lattice parameters a = 5.01313(6) Angstrom, b = 8.8007(1) Angstrom, c = 5.52831(7) Angstrom, and beta = 99.6962(6) degrees. Isolated [BO(3)](3-) anionic groups, which are the fundamental building units, are distributed perfectly parallel to each other. It is a typical structure of big birefringent crystals. The overall structure is similar to that of NaSrBO(3), which crystallizes in P2(1)/c. The correlation between these two structures is discussed. The Mg atoms in NaMgBO(3) are used instead of the position of Na in NaSrBO(3), while the Na atoms occupy the position of Sr. Then the directions of the BO(3) triangles are changed to balance the bond valence, which leads to a higher symmetry. They are the first pair of alkali-alkaline earth orthoborates with close space groups by exchange of the cation positions.

The association of anovulation and endometriosis in the infertile female.

Ninety-six infertile patients with endometriosis were studied and their endometriosis staged according to the Revised American Fertility Society Classification. Anovulation was detected in 19% of the 32 patients with Stage 1 disease but in only 3% in the remaining 64 patients with Stage II, III and IV disease. These results show that contrary to traditional belief, anovulation does occur in a significant number of patients with endometriosis, especially in minimal or mild disease.