Ultraviolet photodepletion spectroscopy of dibenzo-18-crown-6-ether complexes with alkali metal cations

Ultraviolet photodepletion spectra of dibenzo-18-crown-6-ether complexes with alkali metal cations (M+-DB18C6, M = Cs, Rb, K, Na, and Li) were obtained in the gas phase using electrospray ionization quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectra exhibited a few distinct absorption bands in the wavenumber region of 35450−37800 cm^(−1). The lowest-energy band was tentatively assigned to be the origin of the S_0-S_1 transition, and the second band to a vibronic transition arising from the “benzene breathing” mode in conjunction with symmetric or asymmetric stretching vibration of the bonds between the metal cation and the oxygen atoms in DB18C6. The red shifts of the origin bands were observed in the spectra as the size of the metal cation in M^+-DB18C6 increased from Li^+ to Cs^+. We suggested that these red shifts arose mainly from the decrease in the binding energies of larger-sized metal cations to DB18C6 at the electronic ground state. These size effects of the metal cations on the geometric and electronic structures, and the binding properties of the complexes at the S_0 and S_1 states were further elucidated by theoretical calculations using density functional and time-dependent density functional theories

Topological Structure of Dense Hadronic Matter

We present a summary of work done on dense hadronic matter, based on the Skyrme model, which provides a unified approach to high density, valid in the large $N_c$ limit. In our picture, dense hadronic matter is described by the {\em classical} soliton configuration with minimum energy for the given baryon number density. By incorporating the meson fluctuations on such ground state we obtain an effective Lagrangian for meson dynamics in a dense medium. Our starting point has been the Skyrme model defined in terms of pions, thereafter we have extended and improved the model by incorporating other degrees of freedom such as dilaton, kaons and vector mesons.Comment: 13 pages, 8 figures, Talk given at the KIAS-APCTP Symposium in Astro-Hadron Physics "Compact Stars: Quest for New States of Dense Matter", November 10-14, 2003, Seoul, Korea, published by World Scientific. Based on talk by B.-Y. Par

Long-term outcomes after revascularization for advanced popliteal artery entrapment syndrome with segmental arterial occlusion

ObjectivesThere are few long-term follow-up studies about the result of revascularization surgery for the treatment of popliteal artery entrapment syndrome (PAES). We performed this retrospective study to analyze the long-term result of revascularization surgery in patients with advanced PAES during the last 16 years.MethodsTwenty-two limbs in 18 consecutive patients with PAES were treated surgically at Seoul National University Hospital between January 1994 and December 2009. The preoperative diagnosis of PAES was made by duplex ultrasonography, three-dimensional computed tomography angiography, magnetic resonance imaging, or conventional angiography. The method of surgical approach was determined by the extent of arterial occlusion in preoperative images.ResultsThe mean age was 31 years old and the majority of patients were men (94%). The chief complaints were claudication in 18 limbs, ischemic rest pain in three limbs, and toe necrosis in one limb. All 22 limbs underwent revascularization for advanced PAES with segmental arterial occlusion. Fourteen limbs underwent musculotendinous section and popliteo-popliteal interposition graft (13 posterior approaches, one medial approach), five femoropopliteal (below-knee) bypasses, one femoro-posterior tibial bypass, and two popliteo-posterior tibial bypasses. All revascularization surgeries were performed with reversed saphenous veins. The overall primary graft patency rates at 1, 3, and 5 years were 80.9%, 74.6%, and 74.6%, respectively. Comparing 5-year graft patency according to the extent of arterial occlusion, patients with occlusion confined to the popliteal artery (n = 14) showed a better patency rate than patients with occlusion extended beyond the popliteal artery (n = 8) with no statistical significance (83.6% vs 53.6%; P = .053). Comparing 5-year graft patency according to the inflow artery, superficial femoral artery inflow (n = 6) showed a worse patency rate than popliteal artery inflow (n = 16) (30.0% vs 85.9%; P = .015).ConclusionIn advanced popliteal entrapment syndrome, longer bypass with superficial femoral artery inflow showed poor long-term graft patency rate. The graft patency rate was excellent in patients whose arterial occlusion was confined to the popliteal artery and treated by popliteal interposition graft with reversed saphenous vein. With these data, we suggest that longer bypass extending beyond the popliteal artery might only be indicated in patients with critical limb ischemia when the extent of disease does not allow short interposition graft