Trapped modes in an infinite or semi-infinite tube with a local enlargement.

Trapped modes in a hard cylindrical tube with a local axisymmetric enlargement or bulge and filled with a uniform acoustic medium is studied. The governing Helmholtz equation in the cylindrical coordinate system is employed to deal with this problem through the domain decomposition method and matching technique. The trapped modes and the corresponding frequencies less than the threshold frequency or cut-off frequency are derived. It is found that in addition to the fundamental mode, the second- and higher-order trapped modes exist and depend on the geometry parameters of the local bulge. The effects of the bulge radius and width on the frequencies are discussed. The local bulge leads to a decrease of the frequencies and the corresponding vibration mode is localized near the bulge. A multimodal analysis is made and frequency band gap of generalized trapped modes is also studied. A frequency band gap depends on the radius of a bulge and is independent of its width. The obtained results can be extended to analyze bound states in quantum wires.

Resonance frequency and mass identification of zeptogram-scale nanosensor based on the nonlocal beam theory.

Free vibration and mass detection of carbon nanotube-based sensors are studied in this paper. Since the mechanical properties of carbon nanotubes possess a size effect, the nonlocal beam model is used to characterize flexural vibration of nanosensors carrying a concentrated nanoparticle, where the size effect is reflected by a nonlocal parameter. For nanocantilever or bridged sensor, frequency equations are derived when a nanoparticle is carried at the free end or the middle, respectively. Exact resonance frequencies are numerically determined for clamped-free, simply-supported, and clamped-clamped resonators. Alternative approximations of fundamental frequency are given in closed form within the relative error less than 0.4%, 0.6%, and 1.4% for cantilever, simply-supported, and bridged sensors, respectively. Mass identification formulae are derived in terms of the frequency shift. Identified masses via the present approach coincide with those using the molecular mechanics approach and reach as low as 10(-24)kg. The obtained results indicate that the nonlocal effect decreases the resonance frequency except for the fundamental frequency of nanocantilever sensor. These results are helpful to the design of micro/nanomechanical zeptogram-scale biosensor.

Local excision after neoadjuvant chemoradiation therapy in advanced rectal cancer: a national multicenter analysis.

BACKGROUND: The aim of the current study was to evaluate the clinical availability of local excision (LE) for advanced rectal cancer without lymph node metastasis after neoadjuvant chemoradiation therapy (nCRT) in Korea. METHODS: From June 2000 to October 2009, 40 patients with cT2-3N0M0 rectal cancer underwent nCRT followed by LE according to a retrospective multicenter analysis. RESULTS: Of the 40 patients, 22 were men and 18 were women. Eighteen patients were cT2, and 22 patients were cT3. The median follow-up duration was 38 months. Three patients (7.5%) had morbidity after LE. Four patients (10%) had recurrence (local recurrence [1 patient] and systemic metastasis [3 patients]). The 3-year disease-free survival rate was 85.9%. Only pCR was a recurrence-related prognostic factor (P = .040). CONCLUSIONS: Although the current study was not a randomized controlled study, LE after nCRT in T2-3N0 rectal cancer patients appears to be a safe and effective treatment, especially in pCR patients.