Synthesis, reactions and structures of telluronium salts

Abstract

Successful radiotherapy relies on accurate dose measurement. Traditional dosimeters such as ion chambers, TLDs and diodes have disadvantages such as relatively long measurement time and poor spatial resolution. These drawbacks become more serious problems for dynamic beams (i.e. with the use of dynamic wedges or even the intensity modulation technique). X-ray film, an integrating dosimeter, may not be associated with the above disadvantages and problems. However, there are several major issues regarding use of x-ray film for routine dosimetry, including the over-response of the film to low-energy photons, variations in the dose response curve (nonlinearity), lack of reproducibility due to variation in processing, etc. This paper addresses the first problem. That is, x-ray film over-responds to low-energy photons (energies below 400 keV), and thus generates unacceptably inaccurate dosimetric data compared with ion-chamber data.To overcome the over-response problem of x-ray film in a phantom, a scintillation method has been investigated. In this method, a film is sandwiched by two plastic scintillation screens to enhance the film response to upstream electrons, and therefore minimize the over-response caused by low-energy photons. The sandwiched system was tested with a 4 MV linac beam. The result shows that, depending on the uniformity of the scintillation screens, the depth-dose distribution obtained from the sandwich system can be made to agree well with that obtained from ion chambers. However, the required high degree of uniformity remains a challenge for the scintillation screen manufacturers.

Heterocations in Superacid Systems

“…271 Diaryltellurium difluorides also serve as convenient and versatile starting materials to obtain various telluronium tetrafluoroborates 288 (Scheme 4.9). 271 Diaryltellurium difluorides also serve as convenient and versatile starting materials to obtain various telluronium tetrafluoroborates 288 (Scheme 4.9).…”

“…,271 However, acidic selenonium and telluronium ions can be obtained only under superacidic conditions. The salt is stable at 195 K but decomposes within minutes at 213 K to reform the starting materials.The parent hydrotelluronium ion H 3 Te þ could not be observed in superacid solution of hydrogen telluride, under conditions where the selenonium ion is observed.…”

Statistical thermodynamics of binary systems with variable valent states of one of the components

“…Equilibrium distributions of the system are described by Eqs. (9) with obvious changes due to the indicated redefinitions in Eqs. (12)-(14):…”

Generalized lattice model of multicomponent equilibrium and nonequilibrium systems

“…T he generalized lattice model (GLM) of multicomponent condensed systems (such as solid or liquid solutions) was proposed in papers [1,2] and developed [3][4][5][6]. In contradistinction to usual lattice model (see, e.g., Refs.…”