Optimization problem for extremals of the trace inequality in domains with holes

We study the Sobolev trace constant for functions defined in a bounded domain \O that vanish in the subset $A.$ We find a formula for the first variation of the Sobolev trace with respect to hole. As a consequence of this formula, we prove that when \O is a centered ball, the symmetric hole is critical when we consider deformation that preserve volume but is not optimal for some case.Comment: 13 page

Revenue decentralization, central oversight and the political budget cycle : evidence from Israel

This paper examines whether revenue decentralization and direct external financial supervision affect the incidence and strength of political budget cycles, using a panel of Israeli municipalities during the period 1999-2009. We find that high dependence on central government transfers—as reflected in a low share of locally raised revenues in the municipality’s budget—exacerbates political budget cycles, while tight monitoring—exercised through central government appointment of external accountants to debt accumulating municipalities—eliminates them. These results suggest that political budget cycles can result from fiscal institutions that create soft budget constraints: that is, where incumbents and rational voters can expect that the costs of pre-election expansions will be partly covered later by the central government

The Mark Coventry Award: In Vivo Knee Forces During Recreation and Exercise After Knee Arthroplasty

Knee forces directly affect arthroplasty component survivorship, wear of articular bearing surfaces, and integrity of the bone-implant interface. It is not known which activities generate forces within a range that is physiologically desirable but not high enough to jeopardize the survivorship of the prosthetic components. We implanted three patients with an instrumented tibial prosthesis and measured knee forces and moments in vivo during exercise and recreational activities. As expected, stationary bicycling generated low tibial forces, whereas jogging and tennis generated high peak forces. On the other hand, the golf swing generated unexpectedly high forces, especially in the leading knee. Exercise on the elliptical trainer generated lower forces than jogging but not lower than treadmill walking. These novel data allow for a more scientific approach to recommending activities after TKA. In addition, these data can be used to develop clinically relevant structural and tribologic testing, which may result in activity-specific knee designs such as a knee design more tolerant of golfing by optimizing the conflicting needs of increased rotational laxity and conformity