A review of multi-component maintenance models with economic dependence

In this paper we review the literature on multi-component maintenance models with economic dependence. The emphasis is on papers that appeared after 1991, but there is an overlap with Section 2 of the most recent review paper by Cho and Parlar (1991). We distinguish between stationary models, where a long-term stable situation is assumed, and dynamic models, which can take information into account that becomes available only on the short term. Within the stationary models we choose a classification scheme that is primarily based on the various options of grouping maintenance activities: grouping either corrective or preventive maintenance, or combining preventive-maintenance actions with corrective actions. As such, this classification links up with the possibilities for grouped maintenance activities that exist in practice

Tuning fresh: radiation through rewiring of central metabolism in streamlined bacteria

Most free-living planktonic cells are streamlined and in spite of their limitations in functional flexibility, their vast populations have radiated into a wide range of aquatic habitats. Here we compared the metabolic potential of subgroups in the Alphaproteobacteria lineage SAR11 adapted to marine and freshwater habitats. Our results suggest that the successful leap from marine to freshwaters in SAR11 was accompanied by a loss of several carbon degradation pathways and a rewiring of the central metabolism. Examples for these are C1 and methylated compounds degradation pathways, the Entner–Doudouroff pathway, the glyoxylate shunt and anapleuretic carbon fixation being absent from the freshwater genomes. Evolutionary reconstructions further suggest that the metabolic modules making up these important freshwater metabolic traits were already present in the gene pool of ancestral marine SAR11 populations. The loss of the glyoxylate shunt had already occurred in the common ancestor of the freshwater subgroup and its closest marine relatives, suggesting that the adaptation to freshwater was a gradual process. Furthermore, our results indicate rapid evolution of TRAP transporters in the freshwater clade involved in the uptake of low molecular weight carboxylic acids. We propose that such gradual tuning of metabolic pathways and transporters toward locally available organic substrates is linked to the formation of subgroups within the SAR11 clade and that this process was critical for the freshwater clade to find and fix an adaptive phenotype.This work was supported by the Swedish Research Council (Grant Numbers 2012-4592 to AE and 2012-3892 to SB) and the Communiy Sequencing Programme of the US Department of Energy Joint Genome Institute. The work conducted by the US Department of Energy Joint Genome Institute, a DOE Office of Science User Facility, is supported under Contract No. DE-AC02-05CH11231

Seasonal dynamics of active SAR11 ecotypes in the oligotrophic Northwest Mediterranean Sea

A seven-year oceanographic time series in NW Mediterranean surface waters was combined with pyrosequencing of ribosomal RNA (16S rRNA) and ribosomal RNA gene copies (16S rDNA) to examine the environmental controls on SAR11 ecotype dynamics and potential activity. SAR11 diversity exhibited pronounced seasonal cycles remarkably similar to total bacterial diversity. The timing of diversity maxima was similar across narrow and broad phylogenetic clades and strongly associated with deep winter mixing. Diversity minima were associated with periods of stratification that were low in nutrients and phytoplankton biomass and characterised by intense phosphate limitation (turnover time80%) by SAR11 Ia. A partial least squares (PLS) regression model was developed that could reliably predict sequence abundances of SAR11 ecotypes (Q2=0.70) from measured environmental variables, of which mixed layer depth was quantitatively the most important. Comparison of clade-level SAR11 rRNA:rDNA signals with leucine incorporation enabled us to partially validate the use of these ratios as an in-situ activity measure. However, temporal trends in the activity of SAR11 ecotypes and their relationship to environmental variables were unclear. The strong and predictable temporal patterns observed in SAR11 sequence abundance was not linked to metabolic activity of different ecotypes at the phylogenetic and temporal resolution of our study

No se fían

It is a standard practice to test for the signature of homologous recombination in studies examining the genetic diversity of bacterial populations. Although it has emerged that homologous recombination rates can vary widely between species, comparing the results from different studies is made difficult by the diversity of estimation methods used. Here, Multi Locus Sequence Typing (MLST) datasets from a wide variety of bacteria and archaea are analyzed using the ClonalFrame method. This enables a direct comparison between species and allows for a first exploration of the question whether phylogeny or ecology is the primary determinant of homologous recombination rate

Homozigot beta talasemili olgularda immun fonksiyonlar

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.ÖZET Homozigot beta talasemili olgulann prognozunda sık ve düzenli kan transfüzyoriu ile şelasyon sağaltımlarının uygulamaya girmesi ile belirgin düzelme olmuştur. Ancak yaşam süresinin uzaması ile birlikte hastalığa ve sağaltıma ait komplikasyonlar gündeme gelmiştir. Özellikle transfüzyonlarla, ayrıca splenektomi ve demir birikimi ile oluşan immun fonksiyon bozuklukları, enfeksiyonların sıklığı ve şiddeti yönünden, genelde önemli komplikasyonlar olarak yorumlanmaktadır. Biz çalışmamızda, Ege Üniversitesi Tıp Fakültesi Pediatrik Hematoloji Bilim Dalında izlenen, 2 ile 20 yaşlar arasında (ortalama yaş: 9.52 ± 5.38 ), 11 kız, 1 2 erkek, 23 homozigot beta talasemi ve 15 sağlıklı kontrol olgunun hücresel ve humoral immun fonksiyonlarını araştırdık. 10 olguda T hücre, B hücre, CD4, CD8, CD4/CD8, NK, DR+ T hücre, IL-2R, IL-2, JL-7; 23 olguda immun globulinler (IgG, IgM, IgA), IgG subgruplan (IgGı, IgG2, IgG3, IgG4), izohemaglütinin titrajı, IL-3 tayin edildi. Çalışma grubunda hiçbir olguda ağır bir enfeksiyon ya da enfeksiyondan ölüm görülmedi. Hastaların hematolojik parametreleri (lökosit, lenfosit ve nötrofîl sayılan) kontrol grubuna göre belirgin olarak artmıştı ve bu artış hastaların yaşı ve splenektomi uygulanması ile korele idi. Olgularda istatistiksel yönden anlamlı olmasa da, Total T hücre, aktif T hücre, CD4 (+) hücreler ve CD4/CD8 oram daha düşük, NK ise artmış bulundu. Bu bozukluk; 10 yaşından büyük, serum transaminaz, ferritin düzeyleri daha yüksek, yıllık ve transfüzyon sayısı daha fazla ve splenektomi uygulanmış olgularda görüldü. Talasemili hastalarda, serum IL-2 ve IL-2R düzeyleri kontrollere göre anlamlı farklılık göstermedi. Hastalarda görülen kemik iliği eritroid hiperakti vitesi ve 82myeloid seri hücrelerindeki değişikliğe bağlı olarak IL-3 düzeyi artmıştı. IL-7 olgularda azalmıştı ve total T hücre düzeyindeki düşüklük ile uyumlu bulundu. İmmunglobulinlerden, IgG 5 olguda, IgM 8 olguda yüksek bulundu. IgG deki artış, splenektomi ile uyumluluk gösterdi. Hiçbir olguda Ig düzeylerinde düşüklük saptanmadı. İzohemaglütinin düzeyi 1 olguda düşüktü. Bu olguda IgM düzeyinin yaşa göre normal sınırların altında bulunuşu ilginçti. Ig subgruplarmın incelenmesiyle; 15 olguda IgGı, 2 olguda IgG3 düşük bulundu. IgG2 ve IgG4 olguların tümünde normal idi. Bu nedenle talasemili olgularda protein yapısındaki antijenlere antikor yanıtının etkilendiği, polisakkarit yapısmdakilere karşı immun yanıtın normal olduğu düşünüldü. Sonuçta; talasemili olguların hücresel immunitesinde; fonksiyonel değişikliklere yol açmayan sayısal değişiklikler görülmüş, hümöral immunitede ise Ig subgruplanmn etkilendiği kanısına varılmıştı

Scheduling Maintenance and Determining Crew Size for Stochastically Failing Equipment

Past treatment of the single machine maintenance problem has shown that preventive maintenance may be desirable for equipment for which failures are caused at least partially by wear-out factors. In all previous treatment, however, the size of the maintenance-repair crew has been held constant and the optimal maintenance period has then been determined. This paper develops a simultaneous solution for the maintenance-repair crew size and the optimal maintenance period. The optimal maintenance period is seen to shift as the size of the maintenance-repair crew varies. For the multi-machine maintenance problem, the sharing of the maintenance-repair crew creates a queuing system. Because of its complexity, an analytical solution of this multi-machine maintenance queuing system is not feasible. A simulation model was used to develop a set of general rules for scheduling maintenance for the multi-machine case.

Prognostic role of natural killer cells in pediatric mixed cellularity and nodular sclerosing Hodgkin's disease

OBJECTIVE: To study natural killer cells' spontaneous cytotoxic capacity against tumor cells and their prognostic significance in classical Hodgkin's disease