171 research outputs found
Thermal behavior and decomposition kinetics of composite solid propellants in the presence of amide burning rate suppressants
No full textThe employment of burning rate suppressants in the solid rocket propellant formulation is long known. Different research activities have been conducted to well understand the mechanism of suppression, but literature about the action of oxamide (OXA) and azodicarbonamide (ADA) on the thermal decomposition of composite propellant is still scarce. The focus of this study is on investigating the effect of burning rate suppressants on the thermal behavior and decomposition kinetics of composite solid propellants. Thermogravimetric analysis (TG) and differential thermal analysis have been used to identify the changes in the thermal and kinetic behaviors of coolant-based propellants. Two main decomposition stages were observed. It was found that OXA played an inhibition effect on both stages, whereas the ADA acts as a catalyst in the first stage and as coolant in the second one. The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) based on the TG data obtained at different heating rates. The mechanism of action of coolants on the decomposition of solid propellants was confirmed by the kinetic investigation as well
Nanoenergetic Materials
No full textThis highly informative and carefully presented book discusses the preparation, processing, characterization and applications of different types of nanoenergetic materials, as well as the tailoring of their properties. It gives an overview of recent advances of outstanding classes of energetic materials applied in the fields of physics, chemistry, aerospace, defense, and materials science, among others. The content of this book is relevant to researchers in academia and industry professionals working on the development of advanced nanoenergetic materials and their applications
Sliding and abrasive wear behaviour of HVOF- and HVAF-sprayed Cr3C2-NiCr hardmetal coatings
No full textThis paper provides a comprehensive characterisation of HVOF- and HVAF-sprayed Cr3C2-25 wt.% NiCr hardmetal coatings. One commercial powder composition with two different particle size distributions was processed using five HVOF and HVAF thermal spray systems. All coatings contain less Cr3C2 than the feedstock powder, possibly due to the rebound of some Cr3C2-rich particles during high-velocity impact onto the substrate. Dry sand-rubber wheel abrasive wear testing causes both grooving and pull-out of splat fragments. Mass losses depend on inter- and intra-lamellar cohesion, being higher (≥70 mg after a wear distance of 5904 m) for the coatings deposited with the coarser feedstock powder or with one type of HVAF torch. Sliding wear at room temperature against alumina involves shallower abrasive grooving, small-scale delamination and carbide pull-outs, and it is controlled by intra-lamellar cohesion. The coatings obtained from the fine feedstock powder exhibit the lowest wear rates (≈5×10-6 mm3/(Nm)). At 400 °C, abrasive grooving dominates the sliding wear behaviour; wear rates increase by one order of magnitude but friction coefficients decrease from ≈0.7 to ≈0.5. The thermal expansion coefficient of the coatings (11.08×10-6 °C-1 in the 30-400 °C range) is sufficiently close to that of the steel substrate (14.23×10-6 °C-1) to avoid macro-cracking
Tribology of HVOF- and HVAF-sprayed WC-10Co4Cr hardmetal coatings: A comparative assessment
No full textThis paper provides a comprehensive assessment of the sliding and abrasive wear behaviour of WC-10Co4Cr hardmetal coatings, representative of the existing state-of-the-art. A commercial feedstock powder with two different particle size distributions was sprayed onto carbon steel substrates using two HVOF and two HVAF spray processes. Mild wear rates of <10-7mm3/(Nm) and friction coefficients of ≈0.5 were obtained for all samples in ball-on-disk sliding wear tests at room temperature against Al2O3 counterparts. WC-10Co4Cr coatings definitely outperform a reference electrolytic hard chromium coating under these test conditions. Their wear mechanisms include extrusion and removal of the binder matrix, with the formation of a wavy surface morphology, and brittle cracking. The balance of such phenomena is closely related to intra-lamellar features, and rather independent of those properties (e.g. indentation fracture toughness, elastic modulus) which mainly reflect large-scale inter-lamellar cohesion, as quantitatively confirmed by a principal component analysis. Intra-lamellar dissolution of WC into the matrix indeed increases the incidence of brittle cracking, resulting in slightly higher wear rates. At 400°C, some of the hardmetal coatings fail because of the superposition between tensile residual stresses and thermal expansion mismatch stresses (due to the difference between the thermal expansion coefficients of the steel substrate and of the hardmetal coating). Those which do not fail, on account of lower residual stresses, exhibit higher wear rates than at room temperature, due to oxidation of the WC grains.The resistance of the coatings against abrasive wear, assessed by dry sand-rubber wheel testing, is related to inter-lamellar cohesion, as proven by a principal component analysis of the collected dataset. Therefore, coatings deposited from coarse feedstock powders suffer higher wear loss than those obtained from fine powders, as brittle inter-lamellar detachment is caused by their weaker interparticle cohesion, witnessed by their systematically lower fracture toughness as well
Studying the Dynamics of Fc-Engineered Antibodies Using Advanced Imaging Methods
No full textThe past decade has seen an enormous increase in FcRn-targeted engineering strategies to generate antibodies with therapeutic and diagnostic implications. The neonatal Fc receptor, FcRn, is a multifunctional receptor expressed abundantly throughout the body. The trafficking of engineered antibodies in the body is a multiscale process, taking place at subcellular, intracellular, and organ/tissue levels. In this study, various advanced imaging modalities are employed to capitulate the dynamics of Fc-engineered antibodies at different scales. The study investigates the fate of antibody-opsonized tumor cells after phagocytosis in macrophages, an intracellular/micrometer-scale process, using microscopy techniques. Results show a vacuole-like structure associated with the phagosomes exhibiting distinct characteristics. They are lysosomal in nature and impermeable to certain solutes, as seen using fluorescence microscopy analyses. The identification of this vacuole-like compartment has implications for understanding the subsequent processes involved in the degradation of antibody-opsonized tumor cells.
The use of advanced imaging approaches to study subcellular dynamics provides mechanistic insight with excellent spatiotemporal resolution. We imaged the 3D dynamics of two engineered FcRn-inhibitors at the subcellular/nanometer level, using an advanced imaging platform- rMUM. rMUM is capable of imaging the dynamics of the single molecule and the cellular organelles they interact with, in 3D. This enables compensation of the motion of a single molecule with the organelle's movement, thus giving a real snapshot of the dynamics. To that end, we utilized this multi-dimensional, nanometer resolution microscopy technique to image two engineered FcRn-inhibitors in endosomes in cells.
At the macro level, we investigate the effective clearance of antigens by an engineered Fc-antigen fusion protein (HER2-Seldeg), consequently improving contrast during whole-body imaging in mice. HER2-Seldeg is designed to selectively capture anti HER2 antibodies, bind to FcRn with enhanced affinity, and direct them to degradative lysosomes in FcRn-expressing cells. Positron emission tomography (PET) imaging of HER2-Seldeg revealed rapid clearance of radiolabeled antibodies from the systemic circulation following tumor localization and consequently improved contrast
Resarch on children's magazine of Western Trache
No full textYüksek LisansCumhuriyet sonrası Batı Trakya'da yayımlanan dönemin çocuk dergilerini, farklı gazete ve dergi başlığı altında bulunan çocuk ilavelerini bu çalışmamızda tanıtarak incelemeye çalıştık. Batı Trakya'da 1928 sonrası Latin harfleriyle çıkan birçok yayın faaliyeti yanında, çocuk edebiyatına dair eserlerin ilk nüvelerini teşkil eden çocuk dergilerinde bunun en güzel örnekleri verilmiştir. Biz de bu çalışmayla Batı Trakya'da çıkan çocuk dergilerini kapsamlı bir şekilde araştırmamıza dahil ettik. Bu çalışma "Ön Söz", "Giriş", "Sonuç" ve "Kaynakça" dışında iki ana bölümden oluşmaktadır. Giriş kısmı akabinde Batı Trakya'nın tarihsel ve coğrafi yapısıyla, siyasal ve kültürel yapısı hakkında bilgi verdik. Yine Batı Trakya'da geçmişte nihayet bulan ve günümüzde varlığını sürdüren basın faaliyetleri hakkında genel bir çerçeve çizmiş olduk. I. Bölüm'de hem dergilerin tanıtımlarını, güttükleri amaçları, içerik açısından bir incelemesini yapmaya çalıştık, hem de bu dergiler üzerinde çalışma yapmak isteyecek olanlara kolaylık sağlayabilecek bir dizin hazırladık. Biçim bakımından yaptığımız incelemede dergilerin biçim özelliklerini, amacı, yazar kadrosu hakkında bilgi verdik. İçerik incelemesinde ise edebiyat türlerine göre sınıflandırarak incelemeye çalıştık. Bu bölümde yer alan Dizin kısmında da Kronolojik, Yazar Adına Göre (Alfabetik) ve Tematik olarak bir sınıflandırma yaptık. Ayrıca dergilere ait belge niteliğinde olan fotoğrafları Dergilere Ait Belge ve Fotoğraflar başlığı altında bu bölümün sonuna ekledik. Anahtar Kelimeler: Batı Trakya, Çocuk Dergisi, Çocuk Edebiyatı, İncelemeIn this work, I tried to present the journals for children, the sections for children in different newspapers or journals published in Western Thrace region of Greece in Turkish language, after the foundation of the Republic of Turkey. After the Latin alphabet revolution in Turkey in 1928, there were a lot of works published in Western Thrace, including journals for children. At these journals for children, it is possible to see the first examples of children literature in Western Thrace. In this dissertation, I investigated the journals for children published in Western Thrace, adding to my research. Other than the sections of "Preface", "Introduction", "Conclusion" and "Bibliography", this dissertation consists of two main parts. After the introduction part, I gave information about the history, geography, culture and political organisation of Western Thrace. Also, I drew a general picture of different periodically published journals or newspapers, which some of them ceased to exist and others are still continuing to be published. At the first part, I tried to present the journals, explore the goals of them, analyze the content and provide an index to help the future researchers. Regarding my research about the form of journals, I investigated the form, goals, and authors of the journals. On the other hand, in my investigation about the content, I tried to classify them according to the type of literature. At the index section of this part, I classified the literature according to Chronological order, author names (alphabetically) and thematically. I added another section in this part consisting of the photographs of the journals as evidence and named it "Photographs and Documents of the Journals". Key Words: Western Thrace, Children Magazine, Children's Literature, Examinatio
Lifetime measurement of the 6.79 MeV state in [sup 15]O with the AGATA demonstrator
No full textThe N-14(p,gamma)O-15 reaction is the slowest process of the CN cycle, and thus it is of high astrophysical interest since it regulates the total rate of energy and neutrinos production through the cycle. The N-14+p ground state capture is strongly influenced by a sub-threshold resonance corresponding to the 6.79 MeV state in O-15. The width of this resonance is a major source of uncertainty in the extrapolation of the reaction cross section in the Gamow energy window.
Preliminary results of a new Doppler Shift Attenuation measurement of the lifetime of the 6.79 MeV state in O-15 are discussed. The level of interest was populated via the H-2(N-14,n)O-15 reaction in inverse kinematics at 32 MeV beam energy. The gamma-rays emitted in the decay of the 6.79 MeV level to the ground state were detected with the AGATA Demonstrator array of high-purity germanium detectors. The sensitivity of the shape of the peak in the gamma-ray energy spectrum to the level lifetime is investigated comparing the experimental peaks with detailed Monte Carlo simulations of the reaction mechanisms and the gamma-ray emission and detection. Nuclear levels in N-15 (also populated in the N-14+H-2 reaction) for which the lifetimes are known in the literature provided a test of the analysis technique
Imaging Three-Dimensional Single Molecule Dynamics in its Cellular Context
No full textThree-dimensional single molecule microscopy enables the study of dynamic processes in living cells at the level of individual molecules. Multifocal plane microscopy (MUM) is an example of such a modality and has been shown to be capable of capturing the rapid subcellular trafficking of single molecules in thick samples by simultaneously imaging distinct focal planes within the sample. Regardless of the specific modality, however, the obtained 3D trajectories of single molecules often do not fully reveal the biological significance of the observed dynamics. This is because the missing cellular context is often also needed in order to properly understand the events observed at the molecular level. We introduce the remote focusing-MUM (rMUM) modality, which enables 3D single molecule imaging with the simultaneous z-stack imaging of the surrounding cellular structures. Using rMUM, we demonstrate the 3D tracking of prostate-specific membrane antigen (PSMA) with a PSMA-specific antibody in a prostate cancer cell. PSMA is an important biomarker for prostate cancer cells. As such, it is a common target for antibody-based therapies. For example, of particular interest is the use of PSMA-specific antibodies that are conjugated with a toxin that kills prostate cancer cells. We analyze here the pathways of PSMA-specific antibodies, from prior to their first binding to PSMA at the plasma membrane to their arrival at, and continued movement in, sorting endosomes. By making possible the observation of single molecule dynamics within the relevant cellular context, rMUM allows, in our current application, the identification and analysis of different stages of the PSMA-specific antibody trafficking pathway
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