Elastomeric networks based on trimethylene carbonate polymers for biomedical applications : physical properties and degradation behaviour

The number of applications for biomedical technologies is ever-increasing, and there\ud is a need to develop new materials with properties that can conform to the requirements of a\ud specific application. Synthetic polymers are of great importance in the biomedical field as\ud they can be designed to exhibit a wide range of physical- and biological properties and a\ud range of degradation profiles. Interest in biodegradable elastomers is increasing, particularly\ud for the engineering of soft and elastic tissues. These materials are also being utilized more and\ud more for controlled drug delivery purposes.\ud In this thesis, the development of biodegradable elastomers based on trimethylene\ud carbonate polymers using different approaches is presented

Grafen Oksit Ve Polimer Esaslı Nanokompozit Membranların Nefes Figürü Yöntemi Ile Üretilmesi

TÜBİTAK MAG15.10.2017Gözenekli polimerler son yıllarda gaz depolamadan katalize, ayırma süreçlerindenbiyomalzemelere kadar uzanan çok çeşitli alanlarda kullanılmaya başlanmıştır. Bu alanlardanbiri olan ayırma süreçlerine endüstriyel üretimde, doğanın korunmasında ve hatta böbrekrahatsızlıkları gibi bir takım sağlık sorunları ile başa çıkma gibi birçok alanda ihtiyaçduyulmaktadır. Ayırma süreçleri arasında membranla ayırma enerji verimliliği ve düşükmaliyeti sayesinde gittikçe yaygınlaşan bir yöntemdir. Bu projede, en kullanışlı ve düşükmaliyetli gözenekli polimer elde etme yöntemlerinden biri olan nefes figürü yöntemikullanılarak grafen oksit ve polimer esaslı nanokompozit membranların üretimi amaçlanmıştır.Nefes figürü yönteminde gözenekli polimer elde etmek için organik bir çözücüde çözünmüşpolimer çözeltisi (örneğin üzerine nemli hava gönderilerek) nemli ortamda tutulmaktadır.Çözeltideki organik çözücünün buharlaşması ile yüzey sıcaklığında bir düşme gerçekleşir.Bunun sonucunda da çözelti üzerine yollanan nemli hava içerisindeki su çözelti-havaarayüzünde yoğuşur ve yüzeyde dinamik bir şablon görevi gören damlacıklar oluşur. Buyoğuşma sonucu oluşan damlacıklar uygun süreç değişkenleri seçilmesi durumunda düzenlibir dizilim göstermekte ve organik çözücü tamamen buharlaştıktan sonra bal peteğidüzeninde, altıgen dizi şeklinde gözenek yapısına sahip gözenekli polimerler eldeedilebilmektedir.Önerilen araştırmada nefes figürü tekniği kullanılarak gaz ayırmaya yönelik vemikrofiltrasyona yönelik mikroelek yapısında polimer-grafen oksit esaslı iki farklınanokompozit membran üretilmesi planlanmıştır. Membran üretiminde grafen oksitkullanılması i) membranın mukavemetinin arttırılması, ii) su damlacıklarının stabilizasyonu ilegözenek boyutunun kontrolü ve iii) grafen oksitin yapısının değiştirilmesi ile seçiciliğin kontrolügibi avantajları beraberinde getirmektedir. Nefes figürü tekniği ile grafen oksit-polimernanokompozit membranların üretimi de literatüre özgün bir katkı olma özelliği taşımaktadır.Bu membranların üretiminde yüzey alanının ençoklaştırılması ve kabuk tabakanın mümkünolduğunca inceltilmesini sağlayan süreç değişkenleri incelenmiştir.Mikroelek yapısındaki membranlarda polietilen glikol aşılanmış grafen oksitin yüzey aktifmadde olarak kullanılması ve gözenek boyutunun tekil dağılımlı olması amaçlanmıştır. Busayede yüksek akı, düşük kirlenme özelliği gösteren membranlar üretilmesi hedeflenmiştir.Polietilen glikol moleküllerinin hidrofilik özelliklerinden dolayı gözenek çeperinde toplanmasıbeklendiğinden elde edilecek mikroeleklerin kirlenme direncinin yüksek olacağıöngörülmüştür. Ayrıca mikroelek yapısında bulunacak grafen oksit sayesinde mekaniközelliklerin de olumlu yönde gelişmesi planlanmıştır. Yukarıda bahsedilen avantajlarınarağmen, nefes figürü yöntemi ile mikroelek üretiminde polimer aşılanmış grafen oksit henüzkullanılmamıştır. Grafen oksit içeren nanokompozit yapılı polimer mikroeleklerin ?tracketched? ve silikon esaslı mikroeleklere göre üstün özellikleri ve düşük maliyeti olmasıbeklenmektedir. Elde edilen mikroeleklerin mikrofiltrasyona uygunluğu model sistemlerledeğerlendirilmiştir.Her iki uygulamaya yönelik membranların üretiminde bağıl nem oranı, hava akış hızı,polimer/grafen oksit derişimi, substrat türü gibi değişkenlerin elde edilen yapılara etkisiincelenmiştir. Bu projede geliştirilen süreçlerin hem gaz ayırma hem de mikrofiltrasyonalanlarında önemli ilerlemeler sağlamıştır ve elde edilen sonuçların yakın gelecekte ürüneyönelik çalışmalara öncül nitelikte olacağı öngörülmektedir.Recently, porous polymers have found application in various fields extending from gas storageto catalysis and from separation processes to biomaterials. Being one of these fields,separation processes have been needed in industrial production, environmental protection,and in solving health problems such as kidney diseases. Among separation processes,membrane separations is gaining ever increasing use owing to their low cost and energyefficiency. In this Project, breath figüre method as one of the most versatile and low costprocesses for porous polymer production will be utilized to produce graphene oxide polymernanocomposite mebranes. In the breath figüre method, to obtain a porous polymer, a polymersolution in an organic solvent is kept under humid atmosphere (for instance by flowing humidair onto it). The evaporation of the organic solvent in the solution lowers the surfacetemperature of the solution. As a result, the water molecules in humid air condensesat the air-solution interface and water droplets acting as dynamic templates are formed. Underappropriate process conditions, the formed droplets assemble into a periodic pattern andpolymers with hexagonal pore pattern are formed upon evaporation of the solvent.In the proposed research breath figure method will be used to produce two different grapheneoxide-polymer based nanocomposite membranes: on efor gas separation and one havingmicrosieve structure. The use of polymeric films produced by the breath figüre method in gasseparation will be done for the first time. In this part of the project, the skin layer that is formedbetween the substrate and and the water droplet is expected to serve as the gas separationmembrane. Pore walls are expected to servet o strengthen the membrane. The use ofgraphene oxide in membrane production brings the following advantages: i) to increase thestrength of the membrane, ii) stabilization of water droplets and pore size control, iii) controllingthe selectivity of the membrane by adjusting the graphene oxide structure. Production ofgraphene oxide containing nanocomposite membranes via breath figure method is a novelcontribution to literature. In the production of these membranes, the determination of theprocess parameters that give the thinnest skin layer and the largest separation area is targeted.The suitability of obtained membranes for gas separation will be evaluated in model systems.In microsieve structured throughpore membranes, it is targeted to obtain a monodisperse poresize distribution by using poly(ethylene glycol) grafted graphene oxide as a surfactant. In thismanner, it is aimed to produce membranes with high flux and low fouling property. Due to itshydrophilic nature, poly(ethylene glycol) chains are expected to assemble at the pore surface,therefore fouling resistance of the membranes is expected to be high. In addition, the incorporation of graphene oxide into the microsieve structure is expected to increase thestrength of the membranes. Despite the advantages mentioned above, incorporation ofgraphene into microsieve structure in breath figure method has not yet been adopted. Suchmembranes are expected to be more cost effective and show higher performance comparedto track etched or silicon based microsieves. The suitability of the prepared membranes formicrofiltration and their fouling resistance will be studied in model systems.In the production of both types of membranes, parameters such as relative humidity, air flowrate, polymer/graphene oxide concentration, type of substrate will be investigated. Theprocesses to be developed in this project are anticipated to to lead to significant advances ingas separation and microfiltration membranes. The obtained results are expected to beprecursor to product oriented future work

Use of Nanoparticles in Tissue Engineering and Regenerative Medicine

Advances in nanoparticle (NP) production and demand for control over nanoscale systems have had significant impact on tissue engineering and regenerative medicine (TERM). NPs with low toxicity, contrasting agent properties, tailorable characteristics, targeted/stimuli-response delivery potential, and precise control over behavior (via external stimuli such as magnetic fields) have made it possible their use for improving engineered tissues and overcoming obstacles in TERM. Functional tissue and organ replacements require a high degree of spatial and temporal control over the biological events and also their real-time monitoring. Presentation and local delivery of bioactive (growth factors, chemokines, inhibitors, cytokines, genes etc.) and contrast agents in a controlled manner are important implements to exert control over and monitor the engineered tissues. This need resulted in utilization of NP based systems in tissue engineering scaffolds for delivery of multiple growth factors, for providing contrast for imaging and also for controlling properties of the scaffolds. Depending on the application, materials, as polymers, metals, ceramics and their different composites can be utilized for production of NPs. In this review, we will cover the use of NP systems in TERM and also provide an outlook for future potential use of such systems

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Peer reviewe

Measurement of the t(t)over-bar production cross section, the top quark mass, and the strong coupling constant using dilepton events in pp collisions at root s=13TeV

A measurement of the top quark-antiquark pair production cross section sigma(t (t) over bar) in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The data correspond to an integrated luminosity of 35.9 fb(-1), recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events (e(+/-) mu(-/+), mu(+) mu(-), e(+) e(-)) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of m(t)(MC) = 172.5 GeV the fit yields a measured cross section sigma(t (t) over bar) = 803 +/- 2 (stat) +/- 25 (syst) +/- 20 (lumi) pb, in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the POWHEG simulation is performed. The measured value of m(t)(MC) = 172.33 +/- 0.14 (stat)(-0.72)(+0.66) (syst) GeV is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions.Peer reviewe

Measurement of the top quark mass in the all- jets final state at root s=13 TeV and combination with the lepton plus jets channel

A top quark mass measurement is performed using 35.9 fb - 1 of LHC proton- proton collision data collected with the CMS detector at v s = 13 TeV. The measurement uses the tt all- jets final state. A kinematic fit is performed to reconstruct the decay of the tt system and suppress themultijet background. Using the ideogram method, the top quark mass ( mt) is determined, simultaneously constraining an additional jet energy scale factor ( JSF). The resulting value of mt = 172.34 +/- 0.20 ( stat+ JSF) +/- 0.70 ( syst) GeV is in good agreement with previous measurements. In addition, a combined measurement that uses the tt lepton+ jets and all- jets final states is presented, using the same mass extraction method, and provides an mt measurement of 172.26 +/- 0.07 ( stat+ JSF) +/- 0.61 ( syst) GeV. This is the first combined mt extraction from the lepton+ jets and all- jets channels through a single likelihood function.Peer reviewe

Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (μ̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ¯ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ¯ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),μ̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| < 0.03 at 95% confidence level. [Figure not available: see fulltext.

An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe