Akademik Çıktılar

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Citation Count: 48
Amidoxime functionalized Polymers of Intrinsic Microporosity (PIM-1) electrospun ultrafine fibers for rapid removal of uranyl ions from water
(Elsevier Science Bv, 2019) Satilmis, Bekir; Isik, Tugba; Demir, Mustafa M.; Uyar, Tamer; Demir, Mustafa
The Polymers of Intrinsic Microporosity (PIM-1) is considered as one of the most promising polymer candidates for adsorption applications owing to its high surface area and the ability to tailor the functionality for the targeted species. This study reports a facile method for the preparation of amidoxime functionalized PIM-1 fibrous membrane (AF-PIM-FM) by electrospinning technique and its practical use for the extraction of U(VI) ions from aqueous systems via column sorption under continuous flow. Fibrous membrane form of amidoxime functionalized PIM-1 (AF-PIM-FM) was prepared by electrospinning method owing to its excellent processability in dimethylformamide. Bead-free and uniform fibers were obtained as confirmed by SEM imaging and average fiber diameter was 1.69 +/- 0.34 mu m for AF-PIM-FM. In addition, electrospun PIM-1 fibrous membrane (PIM-FM) was prepared as a control group. Structural and thermal characterization of powder and membrane forms of the materials were performed using FT-IR, H-1 NMR, XPS, Elemental analyses, TGA, and DSC. The porosity of the samples was measured by N-2 sorption isotherms confirming amidoxime PIM-1 still maintain their porosity after functionalization. Amidoxime functionality along with membrane structure makes AF-PIM-FM a promising material for uranyl adsorption. First, a comparison between powder and membrane form of amidoxime functionalized PIM-1 was investigated using batch adsorption process. Although membrane form has shown slightly lower adsorption performance in the batch adsorption process, the advantage of using the membrane in column adsorption processes makes membrane form more feasible for real applications. In addition, amidoxime modification enhanced the uranium adsorption ability of PIM-FM up to 20 times. The effect of initial concentration and pH were investigated along with regeneration of the adsorbents. AF-PIM-FM was successfully used for five adsorption-desorption cycles without having any damage on the fibrous structure.
Citation Count: 12
Anomalous transmittance of polystyrene-ceria nanocomposites at high particle loadings
(Royal Soc Chemistry, 2013) Parlak, Onur; Demir, Mustafa M.; Demir, Mustafa
Optical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.
Citation Count: 52
Anti-proliferative, apoptotic and signal transduction effects of hesperidin in non-small cell lung cancer cells
(Springer, 2015) Cincin, Zeynep Birsu; Unlu, Miray; Kiran, Bayram; Bireller, Elif Sinem; Baran, Yusuf; Cakmakoglu, Bedia; Baran, Yusuf
Hesperidin, a glycoside flavonoid, is thought to act as an anti-cancer agent, since it has been found to exhibit both pro-apoptotic and anti-proliferative effects in several cancer cell types. The mechanisms underlying hesperidin-induced growth arrest and apoptosis are, however, not well understood. Here, we aimed to investigate the anti-proliferative and apoptotic effects of hesperidin on non-small cell lung cancer (NSCLC) cells and to investigate the mechanisms involved. The anti-proliferative and apoptotic effects of hesperidin on two NSCLC-derived cell lines, A549 and NCI-H358, were determined using a WST-1 colorimetric assay, a LDH cytotoxicity assay, a Cell Death Detection assay, an AnnexinV-FITC assay, a caspase-3 assay and a JC-1 assay, respectively, all in a time- and dose-dependent manner. As a control, non-cancerous MRC-5 lung fibroblasts were included. Changes in whole genome gene expression profiles were assessed using an Illumina Human HT-12v4 beadchip microarray platform, and subsequent data analyses were performed using an Illumina Genome Studio and Ingenuity Pathway Analyser (IPA). We found that after hesperidin treatment, A549 and NCI-H358 cells exhibited decreasing cell proliferation and increasing caspase-3 and other apoptosis-related activities, in conjunction with decreasing mitochondrial membrane potential activities, in a dose- and time-dependent manner. Through a GO analysis, by which changes in gene expression profiles were compared, we found that the FGF and NF-kappa B signal transduction pathways were most significantly affected in the hesperidin treated NCI-H358 and A549 NSCLC cells. Our results indicate that hesperidin elicits an in vitro growth inhibitory effect on NSCLC cells by modulating immune response-related pathways that affect apoptosis. When confirmed in vivo, hesperidin may serve as a novel anti-proliferative agent for non-small cell lung cancer.
Citation Count: 9
Bioactive sphingolipids in docetaxel-induced apoptosis in human prostate cancer cells
(Elsevier France-editions Scientifiques Medicales Elsevier, 2012) Bassoy, Esen Yonca; Baran, Yusuf; Baran, Yusuf
In this study, we examined the possible roles of ceramide/sphingosine-1-phosphate and ceramide/glucosyleceramide signaling in docetaxel-induced apoptosis by examining expression levels of the glucosyleceramide synthase and sphingosine kinase-1 and ceramide synthase gene family. As confirmed by isobologram analysis, docetaxel in combination with agents that increase intracellular ceramide levels increased the cytotoxic and apoptotic effects of docetaxel synergistically. More importantly, RT-PCR results revealed that expression levels of glucosyleceramide synthase and sphingosine kinase-1 were downregulated and ceramide synthase genes were upregulated in response to docetaxel. This study identifies mechanisms underlying the involvement of ceramide metabolizing genes in docetaxel-induced apoptosis in prostate cancer cells. (c) 2012 Elsevier Masson SAS. All rights reserved.
Citation Count: 42
Bioactive, functional and edible film-forming properties of isolated hazelnut (Corylus avellana L.) meal proteins
(Elsevier Sci Ltd, 2014) Aydemir, Levent Yurdaer; Gokbulut, Aysun Adan; Baran, Yusuf; Yemenicioglu, Ahmet; Baran, Yusuf
This study aimed characterization of bioactive, functional and edible film making properties of isolated proteins from untreated (HPI), hot extracted (HPI-H), acetone washed (HPI-AW), and acetone washed and hot extracted (HPC-AW-H) hazelnut meals. The most bioactive protein extract was HPC-AW-H, followed by HPI-AW, HPI-H and HPI, based on antioxidant activity (TEAC and ORAC: 158-461 mmol Trolox/kg), iron chelation (60.7-126.7 mmol EDTA/kg), angiotensin-converting enzyme inhibition (IC50: 0.57-1.0 mg/mL) and antiproliferative activity on colon cancer cells (IC50: 3.0-4.6 mg/ml). Protein contents of HPI, HPI-H and HPI-AW (93.3-94.5%) were higher than that of HPC-AW-H (86.0%), but HPC-AW-H showed the best pH-solubility profile. The extracts showed good oil absorption (7.4-9.4 g/g) and foaming, but limited water holding and gelling capacities, and emulsion stability. The protein extracts gave transparent, yellowish to brownish and reddish colored and water soluble edible films. The HPI gave the lightest colored films with acceptable mechanical properties (elongation up to 144% and tensile strength up to 4.9 MPa). 1-D and 2-D electrophoresis clearly showed the molecular and isoelectric profiles of hazelnut proteins. The overall results of this study showed that the bioactive, solubility and gelation properties of hazelnut proteins could be improved by simple processes like acetone washing and/or heat treatment. The hazelnut proteins are valuable as multipurpose food ingredients. (c) 2013 Elsevier Ltd. All rights reserved.
Citation Count: 16
Biodiversity, drug discovery, and the future of global health: Introducing the biodiversity to biomedicine consortium, a call to action
(Univ Edinburgh, Global Health Soc, 2017) Neergheen-Bhujun, Vidushi; Awan, Almas Taj; Baran, Yusuf; Bunnefeld, Nils; Chan, Kit; Edison Dela Cruz, Thomas; Kagansky, Alexander; Baran, Yusuf
[No Abstract Available]
Citation Count: 8
BODIPY-based organic color conversion layers for WLEDs
(Elsevier Sci Ltd, 2020) Yuce, Hurriyet; Guner, Tugrul; Dartar, Suay; Kaya, Beraat U.; Emrullahoglu, Mustafa; Demir, Mustafa M.; Demir, Mustafa
The usage of organic dyes in phosphor conversion layer of WLED is an attractive approach since they have high molar extinction coefficient and photostability. Various types of organic pigments have been employed for this purpose such as BODIPY, perylene diimide, Rhodamine B, pyrene, Nile red, etc. Among those, BODIPY-based organic dyes appear to be promising candidate for white light generation. In this work, for the first time, red and green emitting BODIPY-based organic molecules have been used as colour conversion layer. These molecules were associated with PMMA in DMF solution and the resulting solution was subjected to electrospinning. Colorful electrospun mats were embedded into PDMS matrix and their free-standing PDMS composite films were used as color conversion layers over blue LED to produce white light such that CRI of 95 and CCT of 4200 K was achieved. These values show that BODIPY-based organic molecules containing fiber composites are promising candidates to be used as color conversion layers for white light applications.
Citation Count: 24
Characterization investigations during mechanical alloying and sintering of W-20 vol% SiC composites
(Elsevier Science Sa, 2010) Coskun, Selim; Ovecoglu, M. Lutfi; Ozkal, Burak; Tanoglu, Metin; Tanoğlu, Metin
The effect of mechanical alloying and the sintering regime on the microstructural and the physical properties of W-SiC composites were investigated. Powder mixtures of W-20 vol.% SiC were mechanically alloyed (MA'd) using a Spex mill for 3 h, 6 h and 24 h. MA'd powders were characterized by Laser Diffraction Particle Size Analyzer, SEM and XRD investigations. MA'd W-20 vol.% SiC powder composites were sintered under inert Ar and reducing H-2 gas conditions at 1680 degrees C and 1770 degrees C for 1 h. The microstructural and mechanical characterizations of the sintered samples were carried out by scanning electron microscope (SEM) and X-ray diffraction (XRD) and Vickers Hardness analyses. The addition of SiC remarkably increases the hardness of the composites. Hardness is also increased with decreasing grain size and increasing amount of MA. (C) 2009 Elsevier B.V. All rights reserved.
Citation Count: 34
Chemically modified optical fibers in advanced technology: An overview
(Elsevier Sci Ltd, 2019) Shukla, S. K.; Kushwaha, Chandra Shekhar; Guner, Tugrul; Demir, Mustafa M.; Demir, Mustafa
In recent years, chemically modified optical fibers have widely used for development of several advanced chemical and biosensors, biomedical technology and environmental monitoring. The chemically modified optical fiber bears several valuable properties like energy loss, catalytic behaviour, refractive index, and mechanical strength to advance the optical fiber technology. In this article, we reviewed the chemically-modified optical fiber and their applications in different optical fiber-based technologies. The basics of optical fiber and their modification are discussed along with the adopted methodologies. The advancements in different optical fiber based technologies viz sensing, imaging, tomography, magnetic resonance imaging, photodynamic therapy, optogenics, surgery and environmental monitoring are discussed in the light of the contribution of chemically modified optical fibers. In conclusion, success and challenges for the use of chemically modified-optical fiber are presented on the basis of existing literature.
Citation Count: 7
Comparative development of knowledge-based bioeconomy in the European Union and Turkey
(informa Healthcare, 2014) Ozan, Didem Celikkanat; Baran, Yusuf; Baran, Yusuf
Biotechnology, defined as the technological application that uses biological systems and living organisms, or their derivatives, to create or modify diverse products or processes, is widely used for healthcare, agricultural and environmental applications. The continuity in industrial applications of biotechnology enables the rise and development of the bioeconomy concept. Bioeconomy, including all applications of biotechnology, is defined as translation of knowledge received from life sciences into new, sustainable, environment friendly and competitive products. With the advanced research and eco-efficient processes in the scope of bioeconomy, more healthy and sustainable life is promised. Knowledge-based bioeconomy with its economic, social and environmental potential has already been brought to the research agendas of European Union (EU) countries. The aim of this study is to summarize the development of knowledge-based bioeconomy in EU countries and to evaluate Turkey's current situation compared to them. EU-funded biotechnology research projects under FP6 and FP7 and nationally-funded biotechnology projects under The Scientific and Technological Research Council of Turkey (TUBITAK) Academic Research Funding Program Directorate (ARDEB) and Technology and Innovation Funding Programs Directorate (TEYDEB) were examined. In the context of this study, the main research areas and subfields which have been funded, the budget spent and the number of projects funded since 2003 both nationally and EU-wide and the gaps and overlapping topics were analyzed. In consideration of the results, detailed suggestions for Turkey have been proposed. The research results are expected to be used as a roadmap for coordinating the stakeholders of bioeconomy and integrating Turkish Research Areas into European Research Areas.
Citation Count: 81
Critical aspects related to processing of carbon nano tube/unsaturated thermoset polyester nanocomposites
(Pergamon-elsevier Science Ltd, 2007) Seyhan, A. Tugrul; Gojny, Florian H.; Tanoglu, Metin; Schulte, Karl; Tanoğlu, Metin
Carbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix. (c) 2006 Elsevier Ltd. All rights reserved.
Citation Count: 11
Cryopreservation of a cell-based biosensor chip modified with elastic polymer fibers enabling ready-to-use on-site applications
(Elsevier Advanced Technology, 2021) Ozsoylu, Dua; Isik, Tugba; Demir, Mustafa M.; Schoning, Michael J.; Wagner, Torsten; Demir, Mustafa
An efficient preservation of a cell-based biosensor chip to achieve a ready-to-use on-site system is still very challenging as the chip contains a living component such as adherent mammalian cells. Herein, we propose a strategy called on-sensor cryopreservation (OSC), which enables the adherent cells to be preserved by freezing (-80 degrees C) on a biosensor surface, such as the light-addressable potentiometric sensor (LAPS). Adherent cells on rigid surfaces are prone to cryo-injury; thus, the surface was modified to enhance the cell recovery for OSC. It relies on i) the integration of elastic electrospun fibers composed of polyethylene vinyl acetate (PEVA), which has a high thermal expansion coefficient and low glass-transition temperature, and ii) the treatment with O-2 plasma. The modified sensor is integrated into a microfluidic chip system not only to decrease the thermal mass, which is critical for fast thawing, but also to provide a precisely controlled micro-environment. This novel cryo-chip system is effective for keeping cells viable during OSC. As a proof-of-concept for the applicability of a ready-to-use format, the extracellular acidification of cancer cells (CHO-K1) was evaluated by differential LAPS measurements after thawing. Results show, for the first time, that the OSC strategy using the cryo-chip allows label-free and quantitative measurements directly after thawing, which eliminates additional post-thaw culturing steps. The freezing of the chips containing cells at the manufacturing stage and sending them via a cold-chain transport could open up a new possibility for a ready-to-use on-site system.
Citation Count: 11
Design of Polymeric Antiscalants Based on Functional Vinyl Monomers for (Fe, Mg) Silicates
(Amer Chemical Soc, 2017) Topcu, Gokhan; Celik, Asli; Baba, Alper; Demir, Mustafa M.; Demir, Mustafa
Silica/silicate scaling is one of a few detrimental problems that cause high economical loss in the geothermal and petroleum fields. The prevention of silica/silicate has been attempted using antiscalants with functional groups, particularly -NH2; however, metal silicates are commonly found in the fields, and the antiscalants developed thus far are not effective against these compounds. In this work, polymeric antiscalants have been developed by merging two or-snore functional-comonomers consisting of various chelating groups for metal cations. Homo- and copolymers of acrylamide (AM), the sodium salt of vinyl sulfonic acid (VSA), and vinyl phosphonic acid (VPA) were synthesized to examine their antiscaling performance against metal silicate scaling. Lab-scale metal silicates were obtained in a pressured autoclave reactor. The, antiscalants were tested at various dosages (25, 50, and 100 ppm), and their effects were investigated from the leftover decaritates after isolation of the solid precipitates. The polymeric antiscalants were found to be particularly effective against metal silicates and ineffective against simple silica precipitates. Acidic groups may be coordinating the metal cations, which prevents the-formation of precipitates. Among these acidic comonomers; VSA-containing polymers, in particular, increased the solubility-of metal silicates.
Citation Count: 63
Development and characterization of tubular composite ceramic membranes using natural alumino-silicates for microfiltration applications
(Elsevier Science inc, 2015) Ghouil, Boudjemaa; Harabi, Abdelhamid; Bouzerara, Ferhat; Boudaira, Boukhemis; Guechi, Abdelkrim; Demir, Mustafa M.; Figoli, Alberto; Demir, Mustafa
The preparation and characterization of porous tubular ceramic composite microfiltration membranes, using kaolins and calcium carbonates, were reported. The porous gehlenite (2CaO center dot Al2O3 center dot SiO2) and anorthite (CaO center dot Al2O3 center dot 2SiO(2)) based ceramics were obtained by a solid state reaction. A ceramic support, sintered at 1250 degrees C, within an average pore size of about 8 mu m, a porosity of about 47% and a compression strength around 40 MPa, was prepared. The microfiltration active top layer was added on the support by a slip casting from clay powder suspensions. The novel microfiltration membrane layer has a thickness of 40 mu m and an APS value of about 0.2 mu m. This average pore size value was improved and considerably lower than those reported in the literature (0.5 mu m). The performance of the novel microfiltration ceramic membrane was determined for evaluating both the water permeability and rejection. This proved the potentiality of the membrane produced in the microfiltration field. Moreover, the good adhesion, between the support and the active microfiltration layer membranes, was also proved. A correlation between microstructures of used powders and physicochemical properties was discussed. Finally, the origin of the unique two powder order membrane depositions was also proposed. (C) 2015 Elsevier Inc. All rights reserved.
Citation Count: 34
Effect of Molecular Architecture on Cell Interactions and Stealth Properties of PEG
(Amer Chemical Soc, 2017) Ozer, Imran; Tomak, Aysel; Zareie, Hadi M.; Baran, Yusuf; Bulmus, Volga; Baran, Yusuf
PEGylation, covalent attachment of PEG to therapeutic biomolecules, in which suboptimal pharmacokinetic profiles limiting their therapeutic utility are of concern, is a widely applied technology. However, this technology has been challenged by reduced bioactivity of biomolecules upon PEGylation and immunogenicity of PEG triggering immune response and abrogating clinical efficacy, which collectively necessitate development of stealth polymer alternatives. Here we demonstrate that comb-shape poly[oligo(ethylene glycol) methyl ether methacrylate](POEGMA); a stealth polymer alternative, has a more compact structure than PEG and self-organize into nanoparticles in a molecular weight dependent manner. Most notably, we show that comb shape POEGMA promotes significantly higher cellular uptake and exhibits less steric hindrance imposed on the conjugated biomolecule than PEG. Collectively, comb-shape POEGMA offers a versatile alternative to PEG for stealth polymer-biomolecule conjugation applications.
Citation Count: 57
Effect of polyamide-6,6 (PA 66) nonwoven veils on the mechanical performance of carbon fiber/epoxy composites
(Elsevier Sci Ltd, 2018) Beylergil, Bertan; Tanoglu, Metin; Aktas, Engin; Tanoğlu, Metin
In this study, carbon fiber/epoxy (CF/EP) composites were interleaved with polyamide-6,6 (PA 66) nonwoven veils at two different areal weight densities (17 and 50 gsm) to improve their delamination resistance against Mode-I loading. Mode-I fracture toughness (DCB), tensile, open hole tensile (OHT), flexural, compression, short beam shear (ILSS) and Charpy-impact tests were performed on the reference and PA 66 interleaved composite specimens. The DCB test results showed that the initiation and propagation Mode-I fracture toughness values of the composites were significantly improved by 84 and 171% using PA 66-17 gsm veils respectively, as compared to reference laminates. The use of denser PA 66-50 gsm veils in the interlaminar region led to higher improvement in fracture toughness values (349% for initiation and 718% for propagation) due to the higher amount of veil fibers involved in fiber bridging toughening mechanism. The incorporation of PA 66-50 gsm nonwoven veils also increased the ILSS and Charpy impact strength of the composites by 25 and 15%, respectively. On the other hand, the PA 66 veils reduced in-plane mechanical properties of CF/EP composites due to lower carbon fiber volume fraction and increased thickness.
Citation Count: 20
Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties
(Elsevier Sci Ltd, 2010) Yurdakul, Hilmi; Seyhan, A. Tugrul; Turan, Servet; Tanoglu, Metin; Bauhofer, Wolfgang; Schulte, Karl; Tanoğlu, Metin
In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH2 and MWCNT-NH2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature (T-g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T-g than the composites cured without application of the AC electric field. (C) 2010 Elsevier Ltd. All rights reserved.
Citation Count: 0
Enhanced electrocaloric effect of P(VDF-TrFE)-based nanocomposites with Ca and Sn co-doped BaTiO3 particles
(Elsevier Sci Ltd, 2023) Tokkan, Melike; Demir, Mustafa M.; Adem, Umut; Demir, Mustafa
We report on the enhancemenent of electrocaloric effect in solution cast polymer nanocomposites based on Poly (vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE) 55-45] with Ca and Sn co-substituted BaTiO3 ceramic fillers (Ba0.94Ca0.06Ti0.925Sn0.075O3, BCST). Saturated hysteresis loops and normal ferroelectric behaviour of the copolymer-based nanocomposites-as opposed to the relaxor ferroelectric nature of the terpolymer-based ones-allow the utilization of the indirect method to estimate the electrocaloric properties. Both the dielectric constant and electrocaloric temperature change (AT) increases as the particle content increases. Maximum adiabatic temperature change was obtained as 6.96 K under 900 kV/cm for the 10 vol % BCST containing polymer composite around the Curie temperature of the copolymer (70 degrees C). This relatively large electrocaloric strength is slightly lower than those obtained for terpolymer-based nanocomposites.
Citation Count: 24
Ensuring performance and provider profit through data replication in cloud systems
(Springer, 2018) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Bora, Sebnem; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
Cloud computing is a relatively recent computing paradigm that is often the answer for dealing with large amounts of data. Tenants expect the cloud providers to keep supplying an agreed upon quality of service, while cloud providers aim to increase profits as it is a key ingredient of any economic enterprise. In this paper, we propose a data replication strategy for cloud systems that satisfies the response time objective for executing queries while simultaneously enables the provider to return a profit from each execution. The proposed strategy estimates the response time of the queries and performs data replication in a way that the execution of any particular query is still estimated to be profitable for the provider. We show with simulations that how the proposed strategy fulfills these two criteria.
Citation Count: 3
Experimental apparatus for simultaneous measurement of triboelectricity and triboluminescence
(Elsevier Sci Ltd, 2020) Arica, Tugce A.; Topcu, Gokhan; Pala, Atamert; Demir, Mustafa M.; Demir, Mustafa
Triboelectricity is a phenomenon caused by the accumulation of opposite electric charges on the surfaces of two different materials as a result of contact with each other. The phenomenon of emitting cold light when the material is subjected to physical deformation is called triboluminescence. This paper presents an experimental apparatus that allows simultaneous measurement of both triboelectricity and triboluminescence of a model composite system based on poly (vinylidene fluoride) (PVDF) and europium tetrakis (dibenzoylmethide) triethylammonium (EuD(4)TEA). While the former component was studied in contact-separation mode giving triboelectricity, the latter emits triboluminescence upon application of mechanical impact. The device was operated at varying range of frequencies from 0.5 to 4.8 Hz and the force in the range of 5.4-9.5 N. (C) 2019 Elsevier Ltd. All rights reserved.

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