Extremity ring dosimetry intercomparison in reference and workplace fields

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical capabilities of available extremity dosemeters and focusing on their performance at clinical workplaces with potentially high extremity doses. Twenty-four services from 16 countries participated in the intercomparison. The dosemeters were exposed to reference photon (137Cs) and beta (147Pm, 85Kr and 90Sr/90Y) fields together with fields representing realistic exposure situations in interventional radiology (direct and scattered radiation) and nuclear medicine (99 mTc and 18F). It has been found that most dosemeters provided satisfactory measurements of Hp(0.07) for photon radiation, both in reference and realistic fields. However, only four dosemeters fulfilled the established requirements for all radiation qualities. The main difficulties were found for the measurement of low-energy beta radiation. Finally, the results also showed a general under-response of detectors to 18F, which was attributed to the difficulties of the dosimetric systems to measure the positron contribution to the dos

Pressure-induced amorphization and polyamorphism in one-dimensional single crystal TiO2 nanomaterials

The structural phase transitions of single crystal TiO2-B nanoribbons were investigated in-situ at high-pressure using the synchrotron X-ray diffraction and the Raman scattering. Our results have shown a pressure-induced amorphization (PIA) occurred in TiO2-B nanoribbons upon compression, resulting in a high density amorphous (HDA) form related to the baddeleyite structure. Upon decompression, the HDA form transforms to a low density amorphous (LDA) form while the samples still maintain their pristine nanoribbon shape. HRTEM imaging reveals that the LDA phase has an {\alpha}-PbO2 structure with short range order. We propose a homogeneous nucleation mechanism to explain the pressure-induced amorphous phase transitions in the TiO2-B nanoribbons. Our study demonstrates for the first time that PIA and polyamorphism occurred in the one-dimensional (1D) TiO2 nanomaterials and provides a new method for preparing 1D amorphous nanomaterials from crystalline nanomaterials.Comment: 4 figure

Extremity ring dosimetry intercomparison in reference and workplace fields

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical capabilities of available extremity dosemeters and focusing on their performance at clinical workplaces with potentially high extremity doses. Twenty-four services from 16 countries participated in the intercomparison. The dosemeters were exposed to reference photon ((137)Cs) and beta ((147)Pm, (85)Kr and (90)Sr/(90)Y) fields together with fields representing realistic exposure situations in interventional radiology (direct and scattered radiation) and nuclear medicine ((99 m)Tc and (18)F). It has been found that most dosemeters provided satisfactory measurements of H(p)(0.07) for photon radiation, both in reference and realistic fields. However, only four dosemeters fulfilled the established requirements for all radiation qualities. The main difficulties were found for the measurement of low-energy beta radiation. Finally, the results also showed a general under-response of detectors to (18)F, which was attributed to the difficulties of the dosimetric systems to measure the positron contribution to the dose

Phase transitions in yttrium oxide at high pressure studied by Raman spectroscopy

Raman spectra of Y2O3 single crystal were recorded at room temperature in a diamond anvil cell up to a pressure of 22 GPa. Two phase transitions were detected at pressures of 12 and 19 GPa. The different phases were identified with the three structures exhibited by rare-earth (RE) sesquioxides: cubic (C-type), monoclinic (B-type), and rhombohedral (A-type) phases. The first transition corresponds to the C-->B transformation and the second transition to the B-->A transformation. The reversibility of the two phase transitions as well as the evolution of the Y-O bonds under high pressure is discussed. (C) 2000 Elsevier Science Ltd

X-ray absorption near edge structure of quartz. Application to the structure of densified silica

X-ray absorptions spectra of quartz ($10\bar 1 0$), pure silica and densified silica under pressure have been recorded at the silicon and oxygen K-edges. The spectra of quartz show intense polarization effects which have been interpreted on the single scattering approximation, using geometrical considerations. The comparison between the spectra of silica and densified silica, on the basis of this interpretation, gives some information on the structural effect suffered by the silica network under pressure

Cavernous hemangioma of the left forearm

Cavernous hemangiomas are benign hamartomatous proliferation of endothelial tissues. They can arise virtually anywhere in the body and do not contain tissues native to the organ or structure in which they are located. Contrary to what is seen in capillary hemangiomas and the cavernous cutaneous variety, intramuscular hemangiomas almost always never regress. We report a case of intramuscular cavernous hemangioma in an 18-year-old male Nigerian with swelling in the left forearm of 9 years duration. The swelling progressively increased in size and nearly involved the entire forearm with occasional pain and no preceding history of trauma. Pre-operative plain radiographs showed an ill-defined soft tissue swelling with multiple calcifications or phleboliths. Surgical excision with ligation of feeding vessels was done and histology confirmed the diagnosis with free margin of excision. Post-operative clinical improvement was marked

High-pressure and high-temperature study of phase transitions in solid germanium

A detailed investigation of the pressure and temperature dependence of the structure of stable and metastable solid Ge phases in the 0-15 GPa and 295-500 K ranges is presented. Structural results including the equation of state, characteristic of coexistence regions of diamond and P-tin structures, and appearance of metastable phases are discussed and compared with the results presently available in the literature. The isothermal bulk modulus and its derivative are evaluated using temperature-dependent equations of state for Ge I (cubic) and Ge 11 (beta-Sn), and for the Ge III (ST12) metastable polymorph at 400 K