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There is ongoing debate surrounding the roles of surgery and adjuvant radiotherapy in the management of primary and recurrent Merkel cell carcinoma of the head and neck. This study assessed the influence of local excision, margin status, adjuvant radiotherapy and chemotherapy on locoregional recurrence and survival.
A retrospective review of 54 consecutive cases of head and neck Merkel cell carcinoma at a single institution.
Median disease-specific survival time was 120 months. Forty-four per cent of patients developed locoregional recurrence. Combined treatment with surgery and locoregional radiotherapy improved disease-specific survival. Radiotherapy was associated with longer time to recurrence and regional recurrence. Irradiation of the regional nodes improved regional control, irrespective of clinical status. Margin-negative excision was not associated with improved local control. Combined modality treatment of recurrent disease resulted in a four-fold improvement of local control, but small numbers prevented this trend from reaching statistical significance.
Surgical excision of the primary disease and clinically involved regional nodes, plus adjuvant radiotherapy to the surgical bed and regional nodes are recommended for all patients with Merkel cell carcinoma of the head and neck, irrespective of clinical status. Recurrent disease should be aggressively treated with combined modality treatment.
Damage evolution and thermal recovery of 1 MeV Au2+ irradiated samarium titanate pyrochlore (Sm2Ti2O7) single crystals were studied by Rutherford backscattering spectroscopy and nuclear reaction analysis. The damage accumulation follows a nonlinear dependence on dose that is well described by a disorder accumulation model, which indicates a predominant role of defect-stimulated amorphization processes. The critical dose for amorphization at 170 and 300 K is ∼0.14 dpa, and a higher dose of ∼ 0.22 dpa is observed for irradiation at 700 K, which agrees with previous in-situ transmission electron microscopy (TEM) data for polycrystalline Sm2Ti2O7. Annealing in an 18O environment reveals a damage recovery stage at ∼ 850 K that coincides with a significant increase in 18O exchange due to oxygen vacancy mobility. This thermal recovery stage is also consistent with the critical temperature for amorphization measured by in-situ TEM in polycrystalline samples.
We report 1.6 μm emission from InAs QDs (QDs) grown on a GaAs substrate. The ensemble is grown on a graded digital alloy (DA), which increases the matrix lattice constant from 5.65 Å to 5.77 Å. The reduced lattice mismatch between the InAs and matrix material produces larger QDs and thereby allows longer wavelength emission compared to standard growth techniques. The resulting QD density ranges from 2×1010 to 8×1010/cm2 with QD dimensions of 5nm x 30nm measured using atomic force microscopy (AFM). According to x-ray diffraction (XRD) data and transmission electron microscopy (TEM), the metamorphic buffer is unstrained with low defect density.
This chapter illustrates the use of continuum models in control design for stabilizing flexible structures. A 6-degree-of-freedom anisotropic Timoshenko beam with discrete nodes where lumped masses or actuators are located provides a sufficiently rich model to be of interest for mathematical theory as well as practical application. We develop concepts and tools to help answer engineering questions without having to resort to ad hoc heuristic (“physical”) arguments or faith. In this sense the paper is more mathematically oriented than engineering papers and vice versa at the same time. For instance we make precise time-domain solutions using the theory of semigroups of operators rather than formal “inverse Laplace transforms.” We show that the modes arise as eigenvalues of the generator of the semigroup, which are then related to the eigenvalues of the stiffness operator. With the feedback control, the modes are no longer orthogonal and the question naturally arises as to whether there is still a modal expansion. Here we prove that the eigenfunctions yield a biorthogonal Riesz basis and indicate the corresponding expansion. We prove mathematically that the number of eigenvalues is nonfinite, based on the theory of zeros of entire functions. We make precise the notion of asymptotic modes and indicate how to calculate them.