No abstract

Carbon nitride spheres, with diameters ranging from 20 microns to as few as 30 nanometers were prepared by template-directed solid-state or solution reaction of cyanuric chloride or fluoride with lithium nitride. The electron microscopy data on the hollow spheres suggest their multiwalled nanostructure, built by disorderly stacked C 3 N 4 curved layers assembled from triazine rings and nitrogen bridges of pyramidal structure. The closed spherical shape of this form of carbon nitride suggests its use in lubricants, catalyst supports, gas storage, and drug delivery.Carbon nitride (C 3 N 4 ) became an extremely desirable material to produce in view of theoretical predictions 1-5 that the hexagonal (R-and -), cubic (c-) and pseudo-cubic C 3 N 4 polymorphs may possibly be harder than diamond. Many research teams have claimed the observation of tiny micronsize R-, -, and c-C 3 N 4 crystallites in thin films; 6-12 nevertheless, the production of a larger crystals for precise characterization has not been yet accomplished. Graphitic forms of carbon nitride, g-C 3 N 4 , have attracted theoretical 4,5,13-15 and experimental 16-20 attention as well for their potential application as organic semiconductors and precursors for superhard phases.Graphite-like carbon materials are known for their ability to adopt spheroid microstructures, e. g., in fullerenes and their relatives, single-wall and multiwall carbon nanotubes. Substitution of carbon by nitrogen in the planar graphitic structure was predicted to lead to closed forms as well, occurring at N/C atomic ratio greater than 0.2. 21 The possibility of curved structures for carbon nitride phases should be dictated by pyramidal geometry of bridging nitrogen atoms. Indeed, the observations of fullerene-like microstructures 22 and carbon nitride nanotubes 6 of the C 5 N stoichiometry as well as C 3 N 2 nanocage structures in the material with C 3 N 4 bulk composition 23 have been reported. For the nitrogen-rich compositions, such as C 1 N 1 and C 24 N 36 , theoretical calculations also predicted graphitic tubular forms 21,24,25 and a C 60 -derived cage structure, 26 respectively. The PM3 optimization of the molecular cluster with C 24 N 32 composition, 21 which belongs to the C 3 N 4 family, yielded the closed cage structure constructed from the connected eight-membered rings as building blocks resembling arrangement for the -C 3 N 4 phase.

BZA/CE is effective in treating moderate to severe VVA and vaginal symptoms. These data further support the use of a tissue-selective estrogen complex containing BZA/CE as a new menopausal therapy for postmenopausal women.

Estrogen plus progestin relieved some menopausal symptoms, such as vasomotor symptoms and vaginal or genital dryness, but contributed to treatment-related effects, such as bleeding, breast tenderness, and an increased likelihood of gynecologic surgery.