Paired and altruistic kidney donation in the UK: algorithms and experimentation

We study the computational problem of identifying optimal sets of kidney exchanges in the UK. We show how to expand an integer programming-based formulation [1, 19] in order to model the criteria that constitute the UK definition of optimality. The software arising from this work has been used by the National Health Service Blood and Transplant to find optimal sets of kidney exchanges for their National Living Donor Kidney Sharing Schemes since July 2008.We report on the characteristics of the solutions that have been obtained in matching runs of the scheme since this time. We then present empirical results arising from the real datasets that stem from these matching runs, with the aim of establishing the extent to which the particular optimality criteria that are present in the UK influence the structure of the solutions that are ultimately computed. A key observation is that allowing 4-way exchanges would be likely to lead to a significant number of additional transplants

The linear preservers of real diagonalizable matrices

Using a recent result of Bogdanov and Guterman on the linear preservers of pairs of simultaneously diagonalizable matrices, we determine all the automorphisms of the vector space M_n(R) which stabilize the set of diagonalizable matrices. To do so, we investigate the structure of linear subspaces of diagonalizable matrices of M_n(R) with maximal dimension.Comment: 14 page

Nonsimultaneous Chains and Dominos in Kidney- Paired Donation—Revisited

Since 2008, kidney exchange in America has grown in part from the incorporation of nondirected donors in transplant chains rather than simple exchanges. It is controversial whether these chains should be performed simultaneously ‘domino-paired donation’, (DPD) or nonsimultaneously ‘nonsimultaneous extended altruistic donor, chains (NEAD). NEAD chains create ‘bridge donors’ whose incompatible recipients receive kidneys before the bridge donor donates, and so risk reneging by bridge donors, but offer the opportunity to create more transplants by overcoming logistical barriers inherent in simultaneous chains. Gentry et al. simulated whether DPD or NEAD chains would produce more transplants when chain segment length was limited to three transplants, and reported that DPD performed at least as well as NEAD chains. As this finding contrasts with the experience of several groups involved in kidney-paired donation, we performed simulations that allowed for longer chain segments and used actual patient data from the Alliance for Paired Donation. When chain segments of 4–6 transplants are allowed in the simulations, NEAD chains produce more transplants than DPD. Our simulations showed not only more transplants as chain length increased, but also that NEAD chains produced more transplants for highly sensitized and blood type O recipients.Alliance for Paired DonationNovartis (Firm)Genzyme CorporationF. Hoffmann-La Roche & Co.Pfizer Inc.Astellas Pharma USNational Science Foundation (U.S.) (Grant No. 0616733 to the National Bureau of Economic Research)Life Connection of OhioUniversity of Toled

Indicaties, behandeling en resultaat van foleykathetercystostomie bij kleine huisdieren: zes gevallen

Indirect cystostomy is performed to provide urinary diversion in animals with urinary obstruction. Tube cystostomy is a relatively easy technique for rerouting the urine outflow. Four cats and two dogs underwent tube cystostomy with a foleycatheter. The six cases are discussed in a retrospective study. All patients had miction problems due to lower urinary tract disease. The main complication was urinary tract infection. Home care after tube cystostomy was minimal

Deficiency of RgpG causes major defects in cell division and biofilm formation, and deficiency of LytR-CpsAPsr family proteins leads to accumulation of cell wall antigens in culture medium by Streptococcus mutans

ABSTRACT Streptococcus mutans is known to possess rhamnose-glucose polysaccharide (RGP), a major cell wall antigen. S. mutans strains deficient in rgpG , encoding the first enzyme of the RGP biosynthesis pathway, were constructed by allelic exchange. The rgpG deficiency had no effect on growth rate but caused major defects in cell division and altered cell morphology. Unlike the coccoid wild type, the rgpG mutant existed primarily in chains of swollen, “squarish” dividing cells. Deficiency of rgpG also causes significant reduction in biofilm formation ( P &lt; 0.01). Double and triple mutants with deficiency in brpA and/or psr , genes coding for the LytR-CpsA-Psr family proteins BrpA and Psr, which were previously shown to play important roles in cell envelope biogenesis, were constructed using the rgpG mutant. There were no major differences in growth rates between the wild-type strain and the rgpG brpA and rgpG psr double mutants, but the growth rate of the rgpG brpA psr triple mutant was reduced drastically ( P &lt; 0.001). Under transmission electron microscopy, both double mutants resembled the rgpG mutant, while the triple mutant existed as giant cells with multiple asymmetric septa. When analyzed by immunoblotting, the rgpG mutant displayed major reductions in cell wall antigens compared to the wild type, while little or no signal was detected with the double and triple mutants and the brpA and psr single mutants. These results suggest that RgpG in S. mutans plays a critical role in cell division and biofilm formation and that BrpA and Psr may be responsible for attachment of cell wall antigens to the cell envelope. IMPORTANCE Streptococcus mutans , a major etiological agent of human dental caries, produces rhamnose-glucose polysaccharide (RGP) as the major cell wall antigen. This study provides direct evidence that deficiency of RgpG, the first enzyme of the RGP biosynthesis pathway, caused major defects in cell division and morphology and reduced biofilm formation by S. mutans , indicative of a significant role of RGP in cell division and biofilm formation in S. mutans . These results are novel not only in S. mutans , but also other streptococci that produce RGP. This study also shows that the LytR-CpsA-Psr family proteins BrpA and Psr in S. mutans are involved in attachment of RGP and probably other cell wall glycopolymers to the peptidoglycan. In addition, the results also suggest that BrpA and Psr may play a direct role in cell division and biofilm formation in S. mutans . This study reveals new potential targets to develop anticaries therapeutics. </jats:p

Optimal control of the vidale-wolfe-deal and three populations models of market share dynamics

The purpose of this dissertation is to study the optimal response of salesadvertising models for duopolies using modern optimization software (JModelica.org and JuMP). Specifically, the models adopted were the Vidale-Wolfe-Deal and the Three Populations, a Lotka-Volterra type model. Duopoly analysis is split in two parts: one that solves an optimal control problem with the objective of maximizing the net profit of both firms in one-shot, referred to as simultaneous co-operation, and the other that places the two firms as opponents in a sequential game, each with the individual goal of maximizing net profit on its turn, referred to as sequential competition. The contributions of this dissertation are: providing a stability analysis for the Vidale-Wolfe-Deal model, which shows that any control attaining final constant positive values leads to a stable equilibrium of market shares, proposing a duopolistic version of the Three Populations model, and, lastly, proposing and solving a sequential game based on Leader-Follower iteration for the Vidale-Wolfe-Deal model.O propósito desta dissertação é estudar a resposta ótima dos modelos de venda-publicidade em duopólios utilizando modernos software de otimização (JModelica.org e JuMP). Especificamente, os modelos adotados foram Vidale-Wolfe-Deal e Três Populações (um modelo do tipo Lotka-Volterra). As análises de duopólio são divididas em duas partes: uma, que soluciona o problema de controle ótimo com o objetivo de maximizar o lucro líquido de ambas as empresas de uma só vez, referido como cooperação simultânea, e outra, que coloca as duas empresas como oponentes em um jogo sequencial, cada uma com o objetivo individual de maximizar o lucro líquido durante seu turno, referido como competição sequencial. As contribuições da dissertação são: prover análise de estabilidade do modelo Vidale-Wolfe-Deal mostrando que qualquer controle que atinja valores constantes positivos leva a um equilíbrio estável das fatias de mercado, propor uma versão do modelo de Três Populações para o duopólio, e, por fim, propor e solucionar um jogo sequencial baseado em iterações de Líder-Seguidor para o modelo Vidale-Wolfe-Deal

Electrical conductive double-walled carbon nanotubes � Silica glass nanocomposites prepared by the sol�gel process and spark plasma sintering

The electrical conductivity of suspensions in liquid of several kinds of carbon nanotubes (CNTs) is measured. Raw and soft-functionalized double-walled carbon nanotubes (DWCNTs) appear to be the most promising for achieving a low electrical percolation threshold. A 0.35 vol.% DWCNTs�SiO2 nanocomposite is prepared by the sol�gel process and densified by spark plasma sintering. The obtained material presents a fairly good dispersion of DWCNTs and its electrical conductivity (104 S cm1) is six orders of magnitude higher than that previously reported for 1 vol.% multi-walled CNTs�SiO2

Fuzzy Authentication using Rank Distance

Fuzzy authentication allows authentication based on the fuzzy matching of two objects, for example based on the similarity of two strings in the Hamming metric, or on the similiarity of two sets in the set difference metric. Aim of this paper is to show other models and algorithms of secure fuzzy authentication, which can be performed using the rank metric. A few schemes are presented which can then be applied in different scenarios and applications.Comment: to appear in Cryptography and Physical Layer Security, Lecture Notes in Electrical Engineering, Springe