2,091 research outputs found
Error bounds for some semidefinite programming approaches to polynomial minimization on the hypercube.
The Dutch Living Donor Kidney Exchange Program
Kidney transplantation is the optimal option for patients with an end-stage renal
disease. The first successful transplantation with a living genetically related donor
has been performed since 26 October 1954, when an identical twin transplant was
performed in Boston. In the years that followed, efforts to enable non-twin
transplants unfortunately failed because effective immunosuppression was not yet
available. It took until the early sixties after the discovery of azathiopirine that also
deceased donor kidney transplantations became possible. In the eighties of the last
century the wait time for a kidney transplant was approximately one year. Since
that time the success rate of organ transplantation has significantly improved which
attracted large numbers of transplant candidates. As the number of deceased
organ donors did not increase, the wait time on the list steadily grew and at the
moment patients in most Western countries face wait times up to 5 years before a
deceased donor kidney is offered. Unfortunately an increasing proportion of them
will never be transplanted because their clinical situation deteriorates to such an
extent that they are delisted or die on the wait list. For the Netherlands we estimate
that this proportion is approximately 30%. A strategy to expand the kidney donor
pool includes the use of non-heart beating (NHB) donors. Educational programs in
the Netherlands have resulted in an increase in the number of kidney transplants
derived from NHB donors from almost 20% in the year 2000 to 43% in 2004, while
in the years that followed the numbers of NHB donors stabilized. So the NHB
donors have not led to expansion of the deceased kidney donor pool. Possibly
substitution from heart beating to non heart beating donation procedures took
place, resulting from pressure on the facilities of intensive care units. In the
Netherlands, it has been suggested that the main reason for our failure to increase
the number of deceased organ donors is the lack of donor detection. This is
certainly not the case; both in 2005 and in 2006 almost all potential donors in the
Netherlands (96%) were recognized as such and for the vast majority (86%) our
national donor registry was consulted. The problem is not donor detection but the
high refusal rate by the next of kin, which is inherent to our legal system. Our organ
donation act dictates an opt-in system, and therefore all adult citizens are asked to
register their consent for the use of their organ for transplantation purpose after
death. In the Netherlands approximately 25% of the adults are now registered as
potential donors, 15% have explicitly refused and thus for 60% it remains unknown.
Especially in case of potential donors of the latter category high refusal rates up to
70% haven been found. Apparently next of kin argue that while the possibility was
given to everybody to register as donor, their relative did not do so, therefore they
are unaware of consent and thus reluctant to give permission for donation. We feel
that an opt-out organ donation system would be very much helpful to expand the
deceased kidney donor pool. However, we are aware that even if all potential deceased donors became actual donors, there still would be a shortage of donor
kidneys. Therefore the use of kidneys from living donors is an obvious way to go.
These transplants result in a superior unadjusted graft survival compared to
deceased donor kidneys. It has been calculated that the difference in 10 years
survival between living and deceased donor kidney transplantation is 34 %
From research excellence to brand relevance an alternative model for strategic higher education reputation building
Abstract: In this article a novel approach to reputation development at higher education institutions is argued. Global reputation development at higher education institutions is largely driven by research excellence, predominantly measured by research output, and predominantly reflected in hierarchical university rankings which, in turn, is equated with brand equity. It is argued that the current approach to reputation development in higher education institutions is modernist and linear, strangely out of kilter with the complexities of a transforming society in flux, the demands of a diversity of stakeholders, and the drive towards transdisciplinarity, laterality, reflexivity and relevance in science itself. Whilst good research remains an important ingredient of a universityās brand value, a case is made for brand relevance, cocreated in collaboration with stakeholders, as an alternative, non-linear way of differentiation, in light of challenges in strategic science globally, as well as trends and shifts in the emerging paradigm of strategic communication. In applying strategic communication principles to current trends and issues in strategic science and the communication thereof, an alternative model for strategic reputation building at higher education institutions is developed
ACP-EEC CONSULTATIVE ASSEMBLY JOINT COMMITTEE RESOLUTION on cultural cooperation between the ACP States and the EEC.
We consider the problem of minimizing a continuous function f over a compact set K. We compare the hierarchy of upper bounds proposed by Lasserre [Lasserre JB (2011) A new look at nonnegativity on closed sets and polynomial optimization. SIAM J. Optim. 21(3):864ā885] to bounds that may be obtained from simulated annealing. We show that, when f is a polynomial and K a convex body, this comparison yields a faster rate of convergence of the Lasserre hierarchy than what was previously known in the literature
Worst-case examples for Lasserre's measure-based hierarchy for polynomial optimization on the hypercube
We study the convergence rate of a hierarchy of upper bounds for polynomial optimization problems, proposed by Lasserre [SIAM J. Optim. 21(3) (2011), pp. 864-885], and a related hierarchy by De Klerk, Hess and Laurent [SIAM J. Optim. 27(1), (2017) pp. 347-367]. For polynomial optimization over the hypercube, we show a refined convergence analysis for the first hierarchy. We also show lower bounds on the convergence rate for both hierarchies on a class of examples. These lower bounds match the upper bounds and thus establish the true rate of convergence on these examples. Interestingly, these convergence rates are determined by the distribution of extremal zeroes of certain families of orthogonal polynomials
Convergence analysis of a Lasserre hierarchy of upper bounds for polynomial minimization on the sphere
We study the convergence rate of a hierarchy of upper bounds for polynomial minimization problems, proposed by Lasserre (SIAM J Optim 21(3):864ā885, 2011), for the special case when the feasible set is the unit (hyper)sphere. The upper bound at level rāN of the hierarchy is defined as the minimal expected value of the polynomial over all probability distributions on the sphere, when the probability density function is a sum-of-squares polynomial of degree at most 2r with respect to the surface measure. We show that the rate of convergence is O(1/r2) and we give a class of polynomials of any positive degree for which this rate is tight. In addition, we explore the implications for the related rate of convergence for the generalized problem of moments on the sphere
Worst-case Examples for Lasserreās MeasureāBased Hierarchy for Polynomial Optimization on the Hypercube
We study the convergence rate of a hierarchy of upper bounds for polynomial optimization problems, proposed by Lasserre, and a related hierarchy by de Klerk, Hess, and Laurent. For polynomial optimization over the hypercube, we show a refined convergence analysis for the first hierarchy. We also show lower bounds on the convergence rate for both hierarchies on a class of examples. These lower bounds match the upper bounds and thus establish the true rate of convergence on these examples. Interestingly, these convergence rates are determined by the distribution of extremal zeroes of certain families of orthogonal polynomials
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