Structure and Luminescence Properties of Eu3+-Doped Cubic Mesoporous Silica Thin Films

Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration

Computer modeling and description of nonstoichiometric apatites Cd5-η/2(VO4)3I1-η and Cd5-η/2(PO4)3Br1-η as modified chimney-ladder structures with ladder-ladder and chimney-ladder coupling

Diffraction patterns from apatite-structure compounds Cd5-η/2(TO4)3X1-η with T=P, V and X=Br, I show sheets of diffuse scattering normal to c* at incommensurate l=q (q=1.63 for Cd-V-I apatite and q=1.78 for Cd-P-Br apatite), because the c repeat of the average unit cell is shorter than two X diameters. The equilibrium X..X spacing along c defines the incommensurate periodicity c/q and stoichiometry (1-η)=q/2. The layers show a honeycomb texture for the Cd-V-I apatite, which is condensed into discrete spots for the Cd-P-Br compound. In both phases, X..X repulsions along 〈100〉 force neighboring rods of X atoms out of phase. In the Cd-P-Br phase, additional 〈210〉 attractions drive incipient formation of a rhombohedral superstructure. Average structure site occupancies and the observation of second-order diffuse layers at both l=2q and l=q+2 imply the existence of strong Cd..X in addition to X..X interactions. A three-dimensional computer model was used to produce finite-temperature structure simulations as a function of X..X interactions along 〈001〉, 〈100〉, and 〈210〉, and X..Cd interactions, from which diffraction patterns were calculated. The experimental patterns were fit and approximate values for the interaction energies obtained (hundreds to thousands of joules per mole). It was apparent that lock-in to commensurability caused by the X..Cd term and the formation of nonprimitive incommensurate modulated structures driven by X..X interactions were mutually antagonistic, and the actual structures are compromises between the two

Experience with e-PTFE membrane application to bone grafting of cleft maxilla

Previous clinical studies and animal experiments have demonstrated that the placement of expanded polytetrafluoroethylene (e-PTFE) membranes (GORE-TEX®) may be valuable for bone regeneration in nonosteogenic areas. This study aimed to explore the application of this technique to bone grafting of wide alveolopalatal clefts. Ten patients with bilateral clefts were selected and during a 2-week period, all received autogeneic cancellous iliac bone bilaterally. The membrane was placed nasally and orally on the larger cleft side and removed after 3-6 months. All patients have been followed for 14 months. Bone graft incorporation was successful except for one patient (membrane side), who was regrafted 1 year later. However, soft-tissue problems with membrane exposure occurred in the majority of patients, while on the nonmembrane side, healing was uneventful in all cases. Further research in membrane technology is necessary before this method can be accepted for cleft grafting. © 1995 Munksgaard International Publishers Ltd.link_to_subscribed_fulltex

Association between development of lower lip cancer and tobacco habits

Tobacco use is considered to increase the risk of tumor induction. The purpose of this case-controlled investigation was to assess the association of tobacco habits and development of squamous cell carcinoma of the lower lip. Sixty-one patients treated for lower lip cancer, aged between 42 and 90 years, were studied. Age- and sex-matched healthy controls showed a similar exposure to tobacco in years and a comparable distribution of tobacco habits. Although the mean exposure factor (duration times exposure) was greater in the tumor group, no intimate correlation between lip cancer and tobacco was demonstrated. However, an increased, although small, occurrence of herpes labialis lesions was found in cancer patients. The hypothesis is presented that smokers experiencing recurrent herpes simplex virus 1 (HSV-1) infections are more liable to tumor initiation, which issue will be subjected to a future study.</p