No abstract

Although we reported good results of fracture healing, there were functional impairment and a high rate of complications, especially dislocation, in Vancouver B2 and B3 periprosthetic fractures in elderly patients.

Abstract. Habitat preference behavior may play an important role in nonallopatric speciation. However, most examples of habitat preference contributing to differentiation within natural populations correspond to parasites or herbivores living in the discrete environments constituted by their animal or plant hosts. In the present study we investigated migration guided by habitat preference in the intertidal snail Littorina saxatilis in a hybrid zone associated with an ecotone across the shore, which is therefore a continuously varying environment. First, we found evidence for this behavior in one of the two locations studied. Second, we made reciprocal transplants to suppress the phenotypic gradient observed across the hybrid zone and measured the relative contributions of selection and migration to its regeneration. Selection played an important role at the two locations studied, but migration was only important at one, where it accounted for between a third and a half of the regenerated gradient. This overall minor effect of migration was relevant for theoretical models dealing with nonallopatric speciation, because it suggested that variation for habitat preference did not have an important role in the initiation of the differentiation process. The preference behavior observed in the hybrid zone would have evolved secondarily, as a consequence of habitat-dependent fitness differences between phenotypes.

We have analyzed data on the free ion yield observed in liquid isooctane irradiated by 60 Co γ rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian type function and an exponential function.A linear dependence between free ion yield and external electric field has been found at low electric field values (E < 1.2 M V /m) in excellent agreement with the Onsager theory. At higher electric field values we obtain a solution in power series of the external field using the Onsager theory.

A liquid isooctane (C(8)H(18)) filled ionization linear array for radiotherapy quality assurance has been designed, built and tested. The detector consists of 128 pixels, each of them with an area of 1.7 mm x 1.7 mm and a gap of 0.5 mm. The small pixel size makes the detector ideal for high gradient beam profiles such as those present in intensity modulated radiation therapy (IMRT) and radiosurgery. As the read-out electronics we use the X-ray Data Acquisition System with the Xchip developed by the CCLRC. Studies concerning the collection efficiency dependence on the polarization voltage and on the dose rate have been made in order to optimize the device operation. In the first tests, we have studied dose rate and energy dependences. Dose rate dependence was found to be lower than 2.1% up to 5 Gy min(-1), and energy dependence lower than 2.5% up to 20 cm depth in solid water. Output factors and penumbras for several rectangular fields have been measured with the linear array and were compared with the results obtained with a 0.125 cm(3) air ionization chamber and radiographic film, respectively. Finally, we have acquired profiles for an IMRT field and for a virtual wedge. These profiles have also been compared with radiographic film measurements. All the comparisons show a good correspondence. The device has proved its capability to verify on-line therapy beams with good spatial resolution and signal-to-noise ratio.