Low-temperature behaviour of K2Sc[Si2O6]F: determination of the lock-in phase and its relationships with fresnoite- and melilite-type compounds.

K2Sc[Si2O6]F exhibits, at room temperature, a (3 + 2)-dimensional incommensurately modulated structure [a = 8.9878 (1), c = 8.2694 (2) Å, V = 668.01 (2) Å3; superspace group P42/mnm(α,α,0)000s(-α,α,0)0000] with modulation wavevectors q1 = 0.2982 (4)(a* + b*) and q2 = 0.2982 (4)(-a* + b*). Its low-temperature behaviour has been studied by single-crystal X-ray diffraction. Down to 45 K, the irrational component α of the modulation wavevectors is quite constant varying from 0.2982 (4) (RT), through 0.2955 (8) (120 K), 0.297 (1) (90 K), 0.298 (1) (75 K), to 0.299 (1) (45 K). At 25 K it approaches the commensurate value of one-third [i.e. 0.332 (3)]: thus indicating that the incommensurate-commensurate phase transition takes place between 45 K and 25 K. The commensurate lock-in phase of K2Sc[Si2O6]F has been solved and refined with a 3 × 3 × 1 supercell compared with the tetragonal incommensurately modulated structure stable at room temperature. This corresponds to a 3 × 1 × 3 supercell in the pseudo-orthorhombic monoclinic setting of the low-temperature structure, space group P2/m, with lattice parameters a = 26.786 (3), b = 8.245 (2) c = 26.824 (3) Å, ß = 90.00 (1)°. The structure is a mixed tetrahedral-octahedral framework composed of chains of [ScO4F2] octahedra that are interconnected by [Si4O12] rings with K atoms in fourfold to ninefold coordination. Distorted [ScO4F2] octahedra are connected to distorted Si tetrahedra to form octagonal arrangements closely resembling those observed in the incommensurate structure of fresnoite- and melilite-type compounds.

High pressure orthorhombic structure of CuInSe2.

The structural behaviour of CuInSe(2) under high pressure has been studied up to 53 GPa using angle-dispersive x-ray powder diffraction techniques. The previously reported structural phase transition from its ambient pressure tetragonal structure to a high pressure phase with a NaCl-like cubic structure at 7.6 GPa has been confirmed. On further compression, another structural phase transition is observed at 39 GPa. A full structural study of this high pressure phase has been carried out and the high pressure structure has been identified as orthorhombic with space group Cmcm and lattice parameters a = 4.867(8) Å, b = 5.023(8) Å and c = 4.980(3) Å at 53.2(2) GPa. This phase transition behaviour is similar to those of analogous binary and trinary semiconductors, where the orthorhombic Cmcm structure can also be viewed as a distortion of the cubic NaCl-type structure.

X-ray diffraction study of liquid Cs up to 9.8 GPa.

We describe an x-ray diffraction study of liquid Cs at high pressure and temperature conducted in order to characterize the structural changes associated with the complex melting curve and phase transitions observed in the solid phases. At 3.9 GPa we observe a discontinuity in the density of the liquid accompanied by a decrease in the coordination number from about 12 to 8, which marks a change to a nonsimple liquid. The specific volume of liquid Cs, combined with structural analysis of the diffraction data, strongly suggest the existence of dsp(3) electronic hybridization above 3.9 GPa, similar to that reported on compression in the crystalline phase.

Large structural modulations in incommensurate Te-III and Se-IV.

The high-pressure phase of tellurium, Te-III, is found to have an incommensurate monoclinic structure, superspace group I(')2/m(0q0)s0, of a type previously unknown in the elements. Te-III is stable from 4.5(2) to 29.2(7) GPa; the previously reported transition to a distinct Te-IV phase at 10.6 GPa is not observed. The incommensurate wave vector of Te-III is strongly pressure dependent and varies in a strongly nonlinear way. Se-IV is found to be isostructural with Te-III.

Rhino-orbital mucormycosis in a patient with acquired immunodeficiency syndrome (AIDS) and neutropenia.

PURPOSE: To present a case of rhino-orbital mucormycosis in a patient with AIDS and neutropenia managed without exenteration. METHODS: Case report. RESULTS: A 60-year-old African-American man with AIDS developed neutropenia that was probably secondary to antiretroviral therapy. He developed right rhino-orbital mucormycosis and was treated with right partial ethmoidectomy with debridement and liposomal amphotericin B. The infection was cured without need for orbital exenteration, although visual acuity in his right eye ultimately was no light perception. CONCLUSION: Rhino-orbital mucormycosis is uncommon in patients with AIDS. When rhino-orbital mucormycosis occurs, patients require a careful search for an underlying metabolic derangement such as neutropenia. Treatment should be aggressive, but these patients may not require orbital exenteration.

Retinopathy associated with high-dose interferon alfa-2b therapy.

PURPOSE: To present seven patients who developed retinopathy while receiving high-dose interferon alfa-2b therapy for adjuvant treatment of high-risk melanoma. METHODS: Retrospective case series. RESULTS: Seven patients developed a retinopathy while receiving high-dose interferon alfa-2b therapy for adjuvant treatment of high-risk melanoma. Five patients had normal visual acuity, but retinopathy with cotton- wool spots and/or retinal hemorrhages with the retinopathy resolved after stopping treatment after detection. Two patients developed severe retinopathy with vision loss to counting fingers and hand motions without resolution of the retinopathy. The duration of the maintenance treatment before detection of the retinopathy for all patients ranged from 6 to 26 weeks. The total dose received at time of detection of retinopathy ranged from 816 to 1770 million units. Confounding factors included hypertension, thrombocytopenia, anemia, and a history of prior chemotherapy in one patient. Also, one patient received an investigational ganglioside vaccine, one had a history of radiation treatment to the brain, and six received paroxetine. CONCLUSIONS: Patients receiving interferon alfa-2b are at risk for developing an associated retinopathy. The risk appears to be greater with higher dosage therapy. In addition, severe vision loss can be seen with interferon alfa-2b-associated retinopathy. The effect of treatment with selective serotonin reuptake inhibitors, such as paroxetine, in increasing the incidence of this complication is unknown. Patients need to be monitored until the retinopathy is resolved to screen for sequelae, including retinal neovascularization.