The Effect Of Boron Carbide Addition On The Structural And Mechanical Properties Of Tungsten Matrix Composites

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu tezin amacı, mekanik alaşımlama yöntemiyle W-C ve W-B4C-C kompozitlerini sentezlemek ve geliştirmektir. Mekanik alaşımlama ile ağırlıkça %2 bor karbür fazının nanoyapılı volfram matris içerisine dispersoidler olarak dağılması sonucu nanokompozit elde edilmiştir. W-B4C-C (ağ. %1) nanoyapılı kompozitin mekanokimyasal sentez işlemleri 10, 20 ve 30 saat boyunca kuru ve sıvı ortam olmak üzere iki farklı koşulda Spex öğütücü kullanılarak gerçekleştirilmiştir. Bor karbürün etkisini incelemek amacıyla aynı şartlar altında karbür ilavesi kullanılmadan volfram matrisli W-C (ağ. %1) nanokompozitleri üretilmiştir. Mekanik alaşımlanmış volfram esaslı nanoyapılı nanokompozit tozlar, Lazer difraksiyon tane boyut analizi cihazı, Taramalı elektron mikroskobu (SEM) ve X-ışınları difraktometresi (XRD) ile karakterize edilmiştir. Tüm tozlar oda sıcaklığında tek eksenli pres yardımıyla 500 MPa basınç altında preslenmiştir. Numuneler, 1680˚C’de dilatometrede ve 1770˚C’de Linn fırınında hidrojen atmosferi altında sinterlenmiştir. Son aşamada ise nanokompozitlerin yapısal ve mekaniksel özellikleri karakterizasyon incelemeleri ile belirlenmiştir. Bu incelemeler XRD, optik mikroskop, SEM ve Vickers mikrosertlik cihazları kullanılarak gerçekleştirilmiştir. Sinterlenen numunelerin yoğunluğu Arşimet prensibine ve boyutsal analiz yöntemine göre hesaplanmıştır. Yapılan karakterizasyon çalışmaları sonucunda volfram matrisine bor karbür ilavesinin etkileri analiz edilmiştir.The aim of this dissertation work is to synthesize and develop W-C and W-B4C-C composites using mechanical alloying. By using mechanical alloying technique, wt %2 boron carbide phase is distributed homogeneously into tungsten matrix and nanocomposite is obtained. Mechanical and mechanochemical synthesis of W-B4C-C (wt %1) nanocomposite was fabricated by using Spex mixer high energy mill for 10, 20, 30 hours both in dry and wet conditions. To examine the effect of the boron carbide addition, in the same conditions, tungsten matrix composites were produced without using boron carbide. Characterization investigations of the mechanically alloyed nanostructured and nanocomposite tungsten based powders were carried out using Laser Diffraction Particle Size Analyzer, Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD). Powders were cold pressed in the uniaxial hand press machine under 500 MPa pressure at room temperature. Bulk samples were solid phase sintered at 1680 °C in dilatometer and the similar samples were sintered at 1770 °C in Linn furnace under H2 atmosphere. Finally, microstructural and mechanical characterization investigations were applied to the composites. These investigations were carried out by using XRD, optical microscope, SEM and Vickers microhardness machine. Densities of the sintered composites were calculated by using Archimedes principle and dimensional analyses. As a result, the effects of boron carbide addition in the tungsten matrix composites were analyzed.Yüksek LisansM.Sc

Kolorektal adenomlar ve adenokarsinomlarda hücre siklusunu düzenleyen proteinlerin ve apopitozla ilgili belirteçlerin ekspresyonu

OBJECTIVE: Tumor growth is regulated by a balance between proliferation, growth arrest and cell death. In this study, we have examined the expression of p27, cyclin D1, bcl-2, and bcl-x for evaluation of their roles in colon carcinoma progression. MATERIALS and METHODS: The levels of p27, cyclin D1, bcl-2, and bcl-x expression were examined by immunohistochemistry in transitional normal mucosa adjacent to adenomas (n=30), adenomas (n=30), transitional normal mucosa adjacent to adenocarcinomas (n=63), adenocarcinomas (n=63) and metastasis (n=16). Standard streptavidin-biotin immunperoxidase method was used for immunostaining and the stained slides were examined microscopically using semiquantitative criteria. RESULTS: Normal mucosa expressed p27 protein and adenocarcinomas displayed a decrease in the expression of this protein. Decreased expression of p27 was associated with tumor progression (p=0.026). Cyclin D1 staining was prominent in most of the adenocarcinomas and metastasis (p=0.042). Meanwhile, we could not find any relation between p27 and cyclin D1 expression. Bcl-2 and bcl-x expression also did not show any statistically significant correlation in tumor progression. CONCLUSION: The results of this study indicate that reduced p27 and cyclin D1 protein levels play an important role in progression of colon cancer. Bcl-2, and bcl-x expression were of no role.AMAÇ: Tümör gelişimi proliferasyon, büyümede durma ve hücre ölümü arasındaki denge ile düzenlenir. Bu çalışmada, kolon karsinomunun gelişimindeki rollerinin değerlendirilmesinde p27, siklin D1, bcl-2 ve bcl-x expresyonunu inceledik. GEREÇ ve YÖNTEM: p27, siklin D1, bcl-2 ve bcl-x expresyonunun düzeyleri, adenomlara komsu normal mukozada (n=30), adenomlarda (n=30), adenokarsinomlara komsu normal mukozada (n=63), adenokarsinomlarda (n=63) ve metastazlarda (n=16) immünohistokimyasal olarak incelendi. Immün boyama için standart streptavidin-biotin immünperoksidaz metodu kullanıldı ve boyanan slaytlar yarı kantitatif kriterler kullanarak mikroskopik olarak incelendi. BULGULAR: Normal mukozada p27 protein ekspresyonu saptandı, adenokarsinomlar ise bu protein ekspresyonunda azalma gösterdi. p27 ekspresyonunda azalma tümör progresyonu ile ilişkili idi (p=0,026). Siklin D1 boyaması adenokarsinom ve metastazların çoğunda belirgindi (p=0,042). Bu arada, p27 ve siklin D1 ekspresyonu arasında herhangi bir iliski saptamadık. Bcl-2 ve bcl-x ekspresyonu da tümör progresyonunda istatistiksel olarak belirgin anlamlılık göstermedi. SONUÇ: Bu çalışmanın sonucu p27 ve siklin D1 protein düzeylerinin kolon kanserinin progresyonununda önemli rolü oldugunu göstermektedir. Bcl-2 ve bcl-x ekspresyonunun ise rolü saptanmamıştır

Ankara ve çevresinde kuzularda zeranol artık düzeyleri ile serum testesteron, östrojen ve progesterone düzeyleri

Zearalenone'un sentetik bir derivesi olan Zeranol, koyun ve sığırlarda besi performansını artırmak amacıyla anabolik madde olarak kullanılmıştır. Avrupa Birliği ülkelerinde ve Türkiye'de tüketiciye ulaşabilecek kalıntıları nedeniyle hayvanlarda kullanımı yasaklanmıştır. Yasal olmayan kullanımlarında, verilen miktar ve süre bilinmediğinden tesbiti güçtür. Bunun yanında hayvanın yası, cinsi ve bireysel farklılıklar da zeranol'ün vücuttan uzaklaşmasında etkilidir. Bu nedenle hızlı, duyarlı teknikler kullanılmalıdır ve Radioimmunoassay, referans metot olarak önerilmektedir. Ankara çevresinde çiftlik ve mezbahalardan toplanan dışkı ve doku örnelerinde zeranol analizleri ile serum örneklerinde testosteron, progesteron ve östrojen hormon analizleri Radioimmunoassay ile yapılmıştır. Toplam 153 kuzu dışkı örneği zeranol yönünden analiz edildi. Kuzularda % 22 zeranol pozitif bulundu.Zeranol is a synthetic derivative of Zearalenone which has been used as an anabolic substance in sheep and cattle to increase growth of zeranol in food producing animals. The usage of zeranol is prohibited in most countries of the European Union and in Turkey. In the illegal use of zeranol it is difficult to determine its presence because the amount of zeranol given and period is not known. As well as this, the age and breed of the animal plus individual variations affect the period of removal of zeranol from the body. Because of this rapid, sensitive and accurate techniques are needed and Radioimmunoassay (RIA) has been proposed as an reference method for anabolic agent residues.Faeces, serum and tissue samples of lambs from Ankara and the surrounding countryside were collected and the analyses of zeranol, oestrogen, progesteron and testosteron were carried out using Radioimmunoassay. A total of 153 faeces samples of lambs collected from Ankara and the surrounding countryside were analysed for the presence of zeranol positive samples for lamb faeces were 22%

Türkiye’de bulunan üç yarasa türü arasındaki filogenetik ilişkiler

Türkiye’nin farklı iki ilinden örneklenen üç yarasa türünün (Miniopterus schreibersii, Myotis blythii and Myotis myotis) tarif ve tanımlanmasında mitokondrial Cytochrome b geninin kullanılabilirliği test edildi. Morfolojik olarak tanımlanmış olan türler genetik olarak da tanımlandı. Bu çalışma, Türkiye’de biyolojik çeşitliliğin izlenmesi programlarında DNA işaretleyicilerin, değerlendirilebilir moleküler metotlar olduğunu gösterdi. Dizin analizi tabanlı karşılaştırmaların, Türk yarasa türleri ile yapılacak geniş ölçekli çalışmalarda daha fazla esneklik sağlayabileceği sonucuna varıldı.The applicability of DNA sequencing of the Cytochrome b (encoded by mitochondrial DNA) gene was tested for species delineation and species identification in three bat species (Miniopterus schreibersii, Myotis blythii and Myotis myotis) sampled from Turkey as a geographic region. Morphologically identified species have also identified genetically. This study showed that DNA markers are valuable molecular methods for biodiversity monitoring programs in Turkey. Sequencing-based comparisons could provide more flexibility in large-scale studies for Turkish bat species

Genetic analysis of a rabies virus host shift event reveals within-host viral dynamics in a new host

Host shift events play an important role in epizootics as adaptation to new hosts can profoundly affect the spread of the disease and the measures needed to control it. During the late 1990s, an epizootic in Turkey resulted in a sustained maintenance of rabies virus (RABV) within the fox population. Utilisation of Bayesian inferences to investigate whole genome sequences from a cohort of fox and dog brain tissues from Turkey demonstrated that the epizootic occurred in 1997 (+/- 1 year). Furthermore, these data indicate that the epizootic was most likely due to a host shift from locally infected domestic dogs, rather than an incursion of a novel fox or dog RABV. No evidence was detected for virus adaptation to foxes at consensus sequence level; therefore, the deep sequence data was analysed to investigate the influence of sub-consensus populations on host shift events. Viral heterogeneity was measured in all RABV samples; viruses in the early phase after the host shift had increased heterogeneity, in relation to those in the later stage, possibly indicating a role in establishing transmission within a new host. The dynamics of majority and minority variants are consistent with genetic drift, rather than positive selection. The transient expansion of sub-consensus viral populations in the new host species likely represents the virus adapting to a new environment, perhaps due to increased replication within the CNS resulting in a larger population of viruses, or reflecting the lack of host constraints present in the new host reservoir

Evolution of clinical characteristics of patients with paroxysmal nocturnal hemoglobinuria treated with eculizumab in turkey: a multicenter retrospective analysis

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare X-linked genetic disorder. On the contrary to its name, it is a multisystemic disease and various symptoms other than hemoglobinuria could be occurred. It could be life threatening especially because of thromboembolic events. In the last decade, a terminal complement inhibition with eculizumab approved with promising results for PNH patients. We conducted this study to evaluate the long term experience of eculizumab therapy from Turkey for the first time. Our cohort included 138 patients with PNH treated with eculizumab between January 2008 and December 2018 at 28 centers in Turkey. Laboratory and clinical findings at the time of diagnosis and after eculizumab therapy were recorded retrospectively. The median age was 39 (range 18-84) years and median granulocyte PNH clone size was 74% (range 3.06-99.84%) at the time of diagnosis. PNH with bone marrow failure syndrome was detected in 49 patients and the rest of 89 patients had classical PNH. Overall 45 patients (32.6%) had a history of any prior thrombotic event before eculizumab therapy and only 2 thrombotic events were reported during the study period. Most common symptoms are fatigue (75.3%), hemoglobinuria (18.1%), abdominal pain (15.2%) and dysphagia (7.9%). Although PNH is commonly related with coombs negativity, we detected coombs positivity in 2.17% of patients. Seven months after the therapy, increased hemoglobin level was seen and remarkably improvement of lactate dehydrogenase level during the treatment was occurred. In addition to previous studies, our real life data support that eculizumab is well tolerated with no serious adverse events and improves the PNH related findings

The correlates of benefit from neoadjuvant chemotherapy before surgery in non-small-cell lung cancer: a metaregression analysis

Background: Although neoadjuvant chemotherapy (NCT) is widely used, it is not clear which subgroup of locally advanced non-small-cell lung cancer (NSCLC) patients should be treated with this approach, and if a particular benefit associated with NCT exists. In this study, we aimed to investigate the potential correlates of benefit from NCT in patients with NSCLC.Methods: All randomized clinical trials (RCTs) utilizing a NCT arm (without radiotherapy) versus a control arm before surgery were included for metaregression analysis. All regression analyses were weighed for trial size. Separate analyses were conducted for trials recruiting patients with different stages of disease. Previously published measures of treatment efficacy were used for the purpose of this study, regardless of being published in full text or abstract form.Results: A total of 14 RCTs, consisting of 3,615 patients, were selected. Histology, stage, various characteristics of the NCT protocol, and different trial features including trial quality score were not associated with the benefit of NCT. However, in trials of stage 3 disease only, there was a greater benefit in terms of reduction in mortality from NCT, if protocols with three chemotherapeutics were used (B = -0.18, t = -5.25, P = 0.006).Conclusions: We think that patients with stage 3 NSCLC are served better with NCT before surgery if protocols with three chemotherapy agents or equally effective combinations are used. In addition, the effect of neoadjuvant chemotherapy is consistent with regard to disease and patient characteristics. This finding should be tested in future RCTs or individual patient data meta-analyses. © 2012 Bozcuk et al.; licensee BioMed Central Ltd