The Classical and Quantum Lamb Model

In 1900, Horace Lamb considered the classical dynamics of a vibrating particle embedded in an elastic medium. Lamb described how the back action of the elastic waves generated damps the vibrations of the particle. This process is of renewed interest in the quantum regime. The quantum theory of such dissipative systems finds relevance to a variety of mesoscopic and nanoscopic mechanical systems currently under intense experimental study. The Lamb model is revisited here using a Lagrangian framework. The coupling between the vibrating particle and the elastic medium arises from enforcing a holonomic constraint with a Lagrange multiplier. The classical equations of motion, obtained from the Lagrangian, are subsequently solved exactly using integral transform methods. The model is then quantized, and the acoustic power radiated is calculated using time-dependent perturbation theory. These results are valid in the regime of light damping

Sentinel Lymph Node Biopsy in Elderly Patients with Intermediate Thickness Melanoma: A Masters Thesis

Background: A landmark study suggested that wide excision of intermediate-thickness melanoma with sentinel lymph node biopsy (SLNB) and subsequent completion lymph node dissection (CLND) for regional disease may improve prognostication and disease-free survival (DFS) compared with those undergoing wide excision alone. However, these benefits were relatively small and not associated with an improvement in disease-specific survival (DSS). It remains unknown if SLNB and subsequent treatments are beneficial in elderly patients who have a decreased overall (OS) due to other causes. Methods: Adults ≥ 70 years of age, who underwent surgical intervention for intermediate-thickness cutaneous melanoma from 2000-2013 were identified from a prospectively-maintained database. Clinicopathologic variables measured included age, gender, anatomic site, histologic type, tumor thickness, ulceration, receipt and result of SLNB, completion of CLND, OS, and DFS. Results: Ninety-one patients underwent excision of an intermediate-thickness melanoma. Forty-nine patients (54%) received a SLNB. Seven of these biopsies (14%) were positive, and five patients went on to receive CLND. Five-year OS was 41% in patients who did not receive SLNB and 52% in patients who did receive SLNB (p=0.11). DFS was similar between groups independent of receipt of SLNB. Conclusion: Among elderly patients with intermediate-thickness melanoma, patients who received SLNB had similar 5-year OS and DFS compared with those who did not receive SLNB. Routine SLNB for intermediate-thickness melanoma patients may not significantly change outcomes for this age group, and clinical decision-making should consider individual patient comorbidities and goals of care