Designing the Liver Allocation Hierarchy: Incorporating Equity and Uncertainty

Liver transplantation is the only available therapy for any acute or chronic condition resulting in irreversible liver dysfunction. The liver allocation system in the U.S. is administered by the United Network for Organ Sharing (UNOS), a scientific and educational nonprofit organization. The main components of the organ procurement and transplant network are Organ Procurement Organizations (OPOs), which are collections of transplant centers responsible for maintaining local waiting lists, harvesting donated organs and carrying out transplants. Currently in the U.S., OPOs are grouped into 11 regions to facilitate organ allocation, and a three-tier mechanism is utilized that aims to reduce organ preservation time and transport distance to maintain organ quality, while giving sicker patients higher priority. Livers are scarce and perishable resources that rapidly lose viability, which makes their transport distance a crucial factor in transplant outcomes. When a liver becomes available, it is matched with patients on the waiting list according to a complex mechanism that gives priority to patients within the harvesting OPO and region. Transplants at the regional level accounted for more than 50% of all transplants since 2000.This dissertation focuses on the design of regions for liver allocation hierarchy, and includes optimization models that incorporate geographic equity as well as uncertainty throughout the analysis. We employ multi-objective optimization algorithms that involve solving parametric integer programs to balance two possibly conflicting objectives in the system: maximizing efficiency, as measured by the number of viability adjusted transplants, and maximizing geographic equity, as measured by the minimum rate of organ flow into individual OPOs from outside of their own local area. Our results show that efficiency improvements of up to 6% or equity gains of about 70% can be achieved when compared to the current performance of the system by redesigning the regional configuration for the national liver allocation hierarchy.We also introduce a stochastic programming framework to capture the uncertainty of the system by considering scenarios that correspond to different snapshots of the national waiting list and maximize the expected benefit from liver transplants under this stochastic view of the system. We explore many algorithmic and computational strategies including sampling methods, column generation strategies, branching and integer-solution generation procedures, to aid the solution process of the resulting large-scale integer programs. We also explore an OPO-based extension to our two-stage stochastic programming framework that lends itself to more extensive computational testing. The regional configurations obtained using these models are estimated to increase expected life-time gained per transplant operation by up to 7% when compared to the current system.This dissertation also focuses on the general question of designing efficient algorithms that combine column and cut generation to solve large-scale two-stage stochastic linear programs. We introduce a flexible method to combine column generation and the L-shaped method for two-stage stochastic linear programming. We explore the performance of various algorithm designs that employ stabilization subroutines for strengthening both column and cut generation to effectively avoid degeneracy. We study two-stage stochastic versions of the cutting stock and multi-commodity network flow problems to analyze the performances of algorithms in this context

Proper class generated by submodules that have supplements

Thesis (Master)--Izmir Institute of Technology, Mathematics, Izmir, 2008Includes bibliographical references (leaves: 37-38)Text in English: Abstract: Turkish and Englishix, 40 leavesIn this thesis, we study the class S of all short exact sequences 0 A B C 0 where Im& has a supplement in B, i.e. a minimal elemenr in the set {V B V + Im& . B}.The corresponding elements of ExtR(C;A) are called k-elements. In general k-elements need not form a subgroup in ExtR(C;A), but in the category TR of torsion R-modules over a Dedekind domain R, S is a proper class; there are no nonzero S-projective modules and the only S-injective modules are injective R-modules in TR. In this thesis we also give the structure of S-coinjective R-modules in TR. Moreover, we define the class SB of all short exact sequences 0 A B C 0 where Im & has a supplement V in B and V in B and In & is bounded. The corresponding elements of ExtR(C;A) are called B-elements. Over a noetherian integral domain of Krull dimension 1, B-elements form a proper class. In the category TR over a Dedekind domain R, SB is a proper class; there are no nonzero SB-projective R-modules and SB-injective R-modules are only the injective R-modules. In the category TR, reduced SB-coinjective R-modules are bounded R-modules

Depolama Sürecince Bitkisel Yağların Kırmızıbiberin Kalite Parametreleri Üzerine Etkileri

Sunflower, cottonseed, hazelnut, soybean and sesame oils at the concentration of 0, 2, 4 or 6 g/100g red pepper were added into red pepper to determine the effects of the oils on color and oxidative stability during 12-month storage at room temperature. The changes in color, free fatty acid content and peroxide value were determined in 2 month intervals. Initial colors of samples were ranged between 75.26 and 79.95 (ASTA unit), and decreased as the amount of the added vegetable oils increased. Color losses were increased by increasing time for all samples while the color of the soybean oil added samples was more stable. Free fatty acid content and peroxide value of red pepper extracted oils increased significantly as the storage time increased. At the end of storage, free fatty acid content of sesame oil added red pepper was higher than that of others and the lower peroxide value was observed in the control.Ayçiçek, pamuk, fındık, soya ve susam yağları kırmızıbibere 2,4 ve 6 g/100 g kırmızıbiber oranlarında ilave edilmiştir. Yağların, oda sıcaklığında 12 ay süre boyunca renk ve oksidatif stabilite üzerine etkileri araştırılmıştır. Renk, serbest yağ asit içeriği ve peroksit değerlerindeki değişimler 2 aylık periyotlar halinde belirlenmiştir. Başlangıçta örneklerin renk değerleri 75,26-79,95 (ASTA değeri) aralığında bulunmuş ve ilave edilen yağ miktarı artıkça renk değeri düşmüştür. Bütün örneklerde renk kayıpları depolama süresinin artması ile artmış, bununla birlikte soya yağı ilaveli örneklerin renkleri daha stabil olmuştur. Kırmızı biberden ekstrakte edilen yağların serbest yağ asit içerikleri ve peroksit değerleri depolama süresinin artmasıyle önemli ölçüde artmıştır. Depolamanın sonunda susam yağı ilave edilmiş kırmızıbiber örneklerinin serbest yağ asit içerikleri, başlangıç de

Farklı Sıcaklıklarda Depolanan Sütlerin Bazı Fiziko-Kimyasal ve Mikrobiyolojik Özellikleri ile Elekteriksel İletkenlik Arasındaki İlişki

In this research; electrical conductivity ( EC ), pH, lactic acid and total bacteria content of milk were determined. During the storage period at two different temperatures, pH decreased, but lactic acid content and total bacteria increased. The relationship between EC values and these parameters of milk were also investigated. The relation between EC and pH, EC and lactic acid, EC and total bacteria were determined statistically significant (P<0.01). According to the analysis results, a possitive correlation among total bacteria content, lactic acid, and EC values was found, except pH. The results also showed that the electric conductivity can be used for the criteria of milk quality. The presence of lactic acid and pH in milk is important for its quality. Nevertheless, the presence of microorganisms in milk is of great importance for safety of public health.Bu çalışma da, iki farklı depolama sıcaklığında bekletilen sütlerin elektriksel iletkenliği (Eİ), laktik asit, pH ve toplam bakteri içeriği arasındaki ilişki belirlenmiştir. Yapılan çalışma sonucunda farklı sıcaklıkta depolanan sütlerin laktik asit ve toplam bakteri içeriği artarken pH değeri ise azalmıştır. Aynı zamanda çalışmada, bu parametrelerin Eİ ile arasındaki ilişki de araştırılmıştır. Elektriksel iletkenlik ile pH, Eİ ile laktik asit, Eİ ile toplam bakteri arasındaki ilişki istatistiksel olarak önemli bulunmuştur (P<0.01). Yapılan iststistiksel değerlendirmeye göre, pH dışında, Eİ ile laktik asit ve toplam bakteri arasında pozitif bir korelasyon tespit edilmiştir. Bu çalışma sonucunda Eİ’nin süt kalite kriteri olarak kullanılabilir olduğunu göstermiştir. Sütün laktik asit ve pH içeri sütün kalitesi için önemli bununla birlikte, mikroorganizma içeriği ise sağlık güvenliği açısından büyük önem taşımaktadır

İnsanlardan ve hayvanlardan i̇zole edilen blandm-5 üreten karbapenem dirençli escherichia coli kökenlerinin plazmidlerı üstünde bulunan direnç gen tanımlayıcılarının i̇n silico analizi

Due to their ability to resist endpoint antimicrobials such as carbapenem, it is very important to detect and monitor multi-drug resistant Gram negative strains with plasmids containing genes such as blaNDM-5 by new molecular methods. This study aimed to perform in silico analysis of resistance gene identifiers on human and animal-derived blaNDM-5 plasmids found in open databases, which were analyzed by new whole genome sequencing techniques and to compare these resistance genes. The plasmid genomic sequences of 4 human and 2 animal E. coli strains containing blaNDM-5 genes included in our study were analyzed in Silico using the Resistance Gene Identifier (RGI) option of the comprehensive antibiotic resistance gene database using default values. Human and animal strains included in our study were found to have different antimicrobial resistance genes in addition to blaNDM-5. All plasmids were found to have at least 8 perfect antimicrobial resistance gene sequences matches. When the resistance gene identifiers in all plasmids were examined, 35 resistance gene identifiers were found. Besides blaNDM-5, mphA, qacEdelta1 and sul1 were found in all plasmids. As a conclusion, it was determined by our study results that, regardless of the source, there may be different antimicrobial resistance gene identifiers besides the blaNDM-5 resistance gene in plasmids. We are of the opinion that routine molecular surveillance studies should be carried out considering the one health approach of Gram-negative pathogens such as E. coli, which can contain plasmids that cause multi-drug resistance and can be isolated from all sources.Karbapenem gibi son nokta antimikrobiyallere direnç yetenekleri dolayısıyla, blaNDM-5 gibi genler ihtiva eden plazmidlere sahip çoklu ilaç direnci gösteren Gram negatif kökenlerin yeni moleküler yöntemlerle tespiti önemlidir. Biz de çalışmamızda bu yeni tekniklerle tüm genom sekans analizi yapılan ve açık veritabanlarında bulunan insan ve hayvan kaynaklı blaNDM-5 plazmidleri üstünde bulunan direnç gen tanımlayıcılarının in silico analizini yapmayı ve bu direnç genlerini karşılaştırmayı amaçladık. Çalışmamıza dahil edilen 4 insan ve 2 hayvan kaynaklı, blaNDM-5 geni içeren E.coli kökenlerine ait plazmid genomik dizileri, varsayılan değerler kullanılarak kapsamlı antibiyotik direnç gen veritabanının, direnç geni tanımlayıcı (RGI) seçeneği kullanılarak bilgisayar ortamında analiz edildi. Çalışmamıza dahil edilen insan ve hayvan kaynaklı kökenlerde blaNDM-5 yanında farklı antimikrobiyal direnç genlerinin de olduğu tespit edildi. Tüm plazmidlerin en az 8 mükemmel antimikrobiyal direnç gen dizisi eşleşmesi gösterdiği saptandı. Tüm plazmidlerde bulunan direnç gen tanımlayıcıları incelendiğinde 35 direnç gen tanımlayıcısı saptandı. blaNDM-5 yanında, mphA, qacEdelta1 ve sul1’in bütün plazmidlerde olduğu tespit edildi. Sonuç olarak, kaynak fark etmeksizin, plazmidlerde, blaNDM-5 direnç geni yanında farklı antimikrobiyallere direnç gen tanımlayıcılarının da olabildiği çalışma sonucunda tespit edilmiştir. Çoklu ilaç direncine neden olan plazmidleri ihtiva edebilen ve tüm kaynaklardan izole edilebilen E. coli gibi Gram negatif patojenler üzerinde tek sağlık yaklaşımı düşünülerek rutin moleküler surveyans çalışmalarının yapılması gerektiği kanaatindeyiz

What Does Yunus Emre Tell Us?

Having lived 750 years ago, does Yunus Emre have anything to say to the people of today? Were his poems addressed only to the age he lived in, or were they universal? The answer to such questions is "yes". And here is the reason for that: Yunus and his contemporaries speak directly to human beings, touch their hearts and souls and especially address their inner world

Relationship of smartphone use severity with sleep quality, depression, and anxiety in university students

Background and aims The usage of smartphones has increased rapidly in recent years, and this has brought about addiction. The aim of the current study was to investigate the relationship between smartphone use severity and sleep quality, depression, and anxiety in university students. Methods In total, 319 university students (203 females and 116 males; mean age = 20.5 ± 2.45) were included in the study. Participants were divided into the following three groups: a smartphone non-user group (n = 71, 22.3%), a low smartphone use group (n = 121, 37.9%), and a high smartphone use group (n = 127, 39.8%). All participants were evaluated using the Pittsburgh Sleep Quality Index, Beck Depression Inventory, Beck Anxiety Inventory; moreover, participants other than those in the smartphone non-user group were also assessed with the Smartphone Addiction Scale. Results The findings revealed that the Smartphone Addiction Scale scores of females were significantly higher than those of males. Depression, anxiety, and daytime dysfunction scores were higher in the high smartphone use group than in the low smartphone use group. Positive correlations were found between the Smartphone Addiction Scale scores and depression levels, anxiety levels, and some sleep quality scores. Conclusions The results indicate that depression, anxiety, and sleep quality may be associated with smartphone overuse. Such overuse may lead to depression and/or anxiety, which can in turn result in sleep problems. University students with high depression and anxiety scores should be carefully monitored for smartphone addiction