Vascular surgery training in the United States, 1994 to 2003

ObjectiveThe purpose of this study was to analyze the use of operative training resources for vascular surgery residents (VSRs) and general surgery residents (GSRs) over the past 10 years in the United States, to address questions concerning adequate endovascular versus open surgical training and the potential to expand the number of VSRs to meet future workforce needs.MethodsNational operative data from the Residency Review Committee for Surgery (RRC) were analyzed for all vascular surgery (VS) and general surgery (GS) training programs from 1994 to 2003. GSR experience in programs with and without associated VS programs was also compared.ResultsMean total VS volume per VSR increased from 220 operations in 1994 to 368 in 2003, owing to the addition of 140 endovascular procedures by 2003. GSR volume was more stable, with 117 mean total VS operations in 1994 and 122 in 2003. This volume was distributed as approximately 50% major open VS operations for both VSR and GSR. In addition, 39% of VSR experience was endovascular, whereas 32% of GSR experience was vascular access. The average VSR performed 2.7 times more major open VS operations than each GSR, but because of the 10-fold greater number of GSRs, VSRs performed only 20% of the total major operations available for VS training. Selective procedures, such as renal revascularization and open infrarenal abdominal aortic aneurysm repair decreased over time, while endovascular abdominal aortic aneurysm repair increased dramatically, accounting for 46% of aortic aneurysm repairs per VSR in 2003. The mean volume of total interventional procedures per VSR in 2003 was 152 diagnostic and 213 therapeutic. GSRs in programs with and without an associated VS program had very similar operative volumes.ConclusionsInterventional procedures have increased VSR operative volume by 50% in recent years, with only a 12% decrease in major open operations. Nearly all VSRs currently meet RRC minimum requirements for open and endovascular procedures. Mean GSR operative volume has been stable, and far exceeds RRC minimum requirements. Based on the number of major open vascular operations available for training in 2003, the current number of VSR positions could be increased by 50% if GSR operative volume was decreased by 15%. However, increased interventional volume would also be required, for which there is competition with other specialties

The ceaseless quest for knowledge: Stef and his collection at Dartmouth

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Basileos Anglorum ;: a study of the life and reign of King Athelstan of England, 924-939.

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Charge on the quantum dot in the presence of tunneling current

The calculation of the charge present in central region of the double barrier structure at non-equilibrium conditions is discussed. We propose here a simple method to calculate non equilibrium Green's functions which allows consistent calculations of retarded and distribution functions. To illustrate the approach we calculate the charge on the quantum dot coupled {\it via} tunnel barriers to two external leads having different chemical potentials $\mu_L$ and $\mu_R$. The obtained results have been compared with other approaches existing in the literature. They all agree in the equilibrium situation and the departures grow with increasing the difference $\mu_L-\mu_R$.Comment: 9 pages, 2 (.eps) figures, to be published in Solid State Commu

Quantum transport through molecular wires

We explore electron transport properties in molecular wires made of heterocyclic molecules (pyrrole, furan and thiophene) by using the Green's function technique. Parametric calculations are given based on the tight-binding model to describe the electron transport in these wires. It is observed that the transport properties are significantly influenced by (a) the heteroatoms in the heterocyclic molecules and (b) the molecule-to-electrodes coupling strength. Conductance ($g$) shows sharp resonance peaks associated with the molecular energy levels in the limit of weak molecular coupling, while they get broadened in the strong molecular coupling limit. These resonances get shifted with the change of the heteroatoms in these heterocyclic molecules. All the essential features of the electron transfer through these molecular wires become much more clearly visible from the study of our current-voltage ($I$-$V$) characteristics, and they provide several key informations in the study of molecular transport.Comment: 8 pages, 4 figure

Cotunneling through quantum dot with even number of electrons

We study an influence of a finite magnetic field on a small spin-degenerate quantum dot with even number of electrons, attached to metallic leads. It is shown that, under certain conditions, the low energy physics of the system can be described by the S=1/2 antiferromagnetic Kondo model.Comment: Contribution to LT-22; to be published in Physica

A Lie-Algebraic Approach To the Kondo Problem

The Kondo problem is studied using the unitary Lie algebra of spin-singlet fermion bilinears. In the limit when the number of values of the spin $N$ goes to infinity the theory approaches a classical limit, which still requires a renormalization. We determine the ground state of this renormalized theory. Then we construct a quantum theory around this classical limit, which amounts to recovering the case of finite $N$.Comment: 3 figure

Quantum Phase Transition in a Multi-Level Dot

We discuss electronic transport through a lateral quantum dot close to the singlet-triplet degeneracy in the case of a single conduction channel per lead. By applying the Numerical Renormalization Group, we obtain rigorous results for the linear conductance and the density of states. A new quantum phase transition of the Kosterlitz-Thouless type is found, with an exponentially small energy scale $T^*$ close to the degeneracy point. Below $T^*$, the conductance is strongly suppressed, corresponding to a universal dip in the density of states. This explains recent transport measurements.Comment: 4 pages, 5 eps figures, published versio