| 21. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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Efficient Millimeter Wave Doherty PA Design Based on a Low-Loss Combiner Synthesis Technique
- 2017
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 27:12, s. 1143-1145
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Tidskriftsartikel (refereegranskat)abstract
- We report on a record-efficient 30-GHz 21-dBm differential Doherty PA designed in a 130-nm SiGe process. The output network is designed using a recently developed combiner synthesis technique. This technique enables impedance inversion and parasitic compensation to be integrated in one compact network. As a result, the combiner loss is reduced with 0.3-0.5 dB compared with a conventional Doherty combiner. The measured collector and power-added efficiencies at 6-dB back-off level are 30% and 24.3%, respectively, which further validates the advantages of the design technique.
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| 22. |
- Özeren, Hüsamettin Deniz
(författare)
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Plasticization of Biobased Polymers: A Combined Experimental and Simulation Approach
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of bio-based plastics has developed significantly in recent decades and there is an increasing demand for industries to shift from petrochemical to biobased polymers. Biobased polymers offer competitive properties, and in many cases have advantages in terms of cost. Thermoplastic starch is already commercially available, while wheat-gluten protein-based materials are considered to be promising candidates for commercial use.Biobased materials can, however, have several drawbacks that have to be handled. Starch-based materials are, in general, brittle due to the stiff glucose-based molecular chain and hydrogen bond network. This is the case also for proteins (due to the stiff peptide bond, bulky side groups and hydrogen bond network), like for example gluten. These issues can, however, be resolved with effective compatible plasticizers. But in order to be able to optimize the choice of the right plasticizer for a specific polymer, there is a need for an increased understanding of the plasticizer mechanisms. Besides, a methodology for prediction of the plasticizer amount needed, as well as to be able to rank possible plasticizer candidates, based on their effectiveness. As a part of the development of a methodology (based on the combination of experimental and molecular-dynamics simulations) for prediction of plasticization and to investigate and understand plasticizer mechanisms, the main material investigated was starch, but also wheat gluten, both plasticized with glycerol. The main plasticizer used to date for biobased polymer materials is glycerol, because of its effectiveness, stability and low cost. In addition, it is also a large byproduct of biodiesel production. A number of other plasticizer candidates were also studied for the starch system to see if the developed methodology could be used to rank plasticizers. Diols were tested in the starch system as plasticizers, but they had no or little plasticization effect. Nevertheless, they gave rise to unexpected structures and properties. Several techniques were used to determine the experimental properties of the bio-based films, including calorimetry, gravimetry, dynamic mechanical analysis, and tensile testing.The results (based on mechanical and thermal properties) showed that the methodology could be used to rank plasticizers in terms of their effectiveness. It was also possible to predict the amount of plasticizer needed for effective softening. With the help of the simulations, the emollient effect could be studied in detail and largely explained by hydrogen bonding effects. The methodology was also developed to be able to predict from simulation not only trends in mechanical properties but also absolute values in stiffness and strength at elongation rates corresponding to experimental measurements.
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| 23. |
- Özgümüs, Türküler, et al.
(författare)
-
Starvation to Glucose Reprograms Development of Neurovascular Unit in Embryonic Retinal Cells
- 2021
-
Ingår i: Frontiers in Cell and Developmental Biology. - : Frontiers Media SA. - 2296-634X. ; 9, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Perinatal exposure to starvation is a risk factor for development of severe retinopathy in adult patients with diabetes. However, the underlying mechanisms are not completely understood. In the present study, we shed light on molecular consequences of exposure to short-time glucose starvation on the transcriptome profile of mouse embryonic retinal cells. We found a profound downregulation of genes regulating development of retinal neurons, which was accompanied by reduced expression of genes encoding for glycolytic enzymes and glutamatergic signaling. At the same time, glial and vascular markers were upregulated, mimicking the diabetes-associated increase of angiogenesis-a hallmark of pathogenic features in diabetic retinopathy. Energy deprivation as a consequence of starvation to glucose seems to be compensated by upregulation of genes involved in fatty acid elongation. Results from the present study demonstrate that short-term glucose deprivation during early fetal life differentially alters expression of metabolism- and function-related genes and could have detrimental and lasting effects on gene expression in the retinal neurons, glial cells, and vascular elements and thus potentially disrupting gene regulatory networks essential for the formation of the retinal neurovascular unit. Abnormal developmental programming during retinogenesis may serve as a trigger of reactive gliosis, accelerated neurodegeneration, and increased vascularization, which may promote development of severe retinopathy in patients with diabetes later in life.
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| 24. |
- Özkaya Sahin, Gülsen, et al.
(författare)
-
Frequent intratype neutralization by plasma immunoglobulin A identified in HIV-2 infection.
- 2013
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Ingår i: AIDS Research and Human Retroviruses. - 1931-8405. ; 29:3, s. 470-478
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Tidskriftsartikel (refereegranskat)abstract
- Human immunodeficiency virus type 2 (HIV-2) is less transmissible and less pathogenic compared to HIV-1 and, when matched for CD4+ T cell count, the plasma viral load in HIV-2 infected individuals is approximately one log lower than in HIV-1 infected individuals. The explanation for these observations is elusive, but differences in virus controlling immunity generated in the two infections may be contributing factors. In the present study, we investigated neutralization by immunoglobulin A (IgA), in parallel with IgG, purified from plasma of HIV-1, HIV-2 and HIV-1/HIV-2 dually (HIV-D)-infected individuals. Neutralization was analyzed against HIV-1 and HIV-2 isolates using a plaque reduction assay. In HIV-2 infection, intratype-specific neutralization by IgA was frequently detected, although at a lesser magnitude then the corresponding IgG neutralizing titers. In contrast, neutralization by IgA could rarely be demonstrated in HIV-1 infection despite similar plasma IgA levels in both infections. In addition, IgA and IgG of HIV-D plasma neutralized the HIV-2 isolate more potently than the HIV-1 isolate, suggesting that the difference between neutralizing activity of plasma IgA and IgG depends on the virus itself. Taken together, these findings suggest that both IgA and IgG adds to the potent intratype neutralizing activity detected in HIV-2 plasma, which may contribute to virus control in HIV-2 infection.
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| 25. |
- Özkirimli, Umut
(författare)
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Homeless
- 2018
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Ingår i: Ahval.
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 26. |
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| 27. |
- Özkirimli, Umut
(författare)
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Nationalism
- 2019
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Ingår i: Oxford Bibliographies.
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Tidskriftsartikel (refereegranskat)
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| 28. |
- Özyagci, Ali, 1982-
(författare)
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Selfish Dynamic Spectrum Access in Multichannel Wireless Networks : Complete and incomplete information analysis
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing popularity and widespread deployment of wireless data systems fuel the increasing demand for more spectrum. On the other hand, various studies measuring spectrum utilization show that there is a huge variation in spectrum utilization at different times and locations. In view of this, various dynamic spectrum access (DSA) methods have been proposed in order to achieve more efficient utilization of spectrum resources by virtue of exploiting the variations in spectrum demand over time and space. Implementing DSA systems in a centralized way can lead to complexity and scalability problems due to the extensive control signaling involved. Therefore distributed implementations of DSA systems in which the users can access the system resources at their own discretion have been proposed. These distributed mechanisms typically incorporate cognitive radio systems which act as agents on behalf of users to measure the radio environment and make decisions based on these measurements. On the other hand, the freedom of the users in distributed systems to form their actions can lead each user to try to maximize its benefit from the system without regard the overall performance of the DSA system. Therefore, selfish behavior can prevail in distributed systems, which is likely to degrade the system performance.In this thesis we investigate the implications of selfish decision making in dynamic spectrum access systems. To address this broad problem, we focus our analysis on a particular system which can represent the essential properties of DSA systems and thus can shed light on the performance of the broad class of DSA systems with selfish users. Specifically, we model a DSA system as a multichannel random access system which uses ALOHA for medium access, and we analyze the behavior of the selfish users by modeling the system as a non-cooperative game. In this analysis we incorporate the effect of channel state information on the decision making of the users; we consider both cases when the users act on global (complete) and on local (incomplete) information. We determine the behavior of the selfish users at the Nash equilibria of the non-cooperative game and measure the performance of the system in terms of sum and individual utilities for various user loads and amount of available resources. We try to identify how the performance of the DSA system with selfish users compares with its cooperative counterpart. By performing these analyses we provide insights into the broader question of whether selfish users can utilize spectrum resources in a DSA system as well as cooperative users.
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| 29. |
- Adler, Niclas, et al.
(författare)
-
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 30. |
- Heshmati, Almas, et al.
(författare)
-
- 2013
-
Ingår i: Research Evaluation. - : Oxford University Press (OUP). - 0958-2029 .- 1471-5449. ; 22:1, s. 15-29
-
Tidskriftsartikel (refereegranskat)abstract
- This article introduces an agent-based simulation model representing the dynamic processes of cooperative R&D in the manufacturing sector of South Korea. Firms’ behaviors were defined according to empirical findings on a data set from the internationally standardized Korean Innovation Survey in 2005. Simulation algorithms and parameters were defined based on the determinants of firms’ likelihood to participate in cooperation with other firms when conducting innovation activities. The calibration process was conducted to the point where artificially generated scenarios were equivalent to the one observed in the real world. The aim of this simulation game was to create a basic implementation that could be extended to test different policies strategies in order to observe sector responses (including cross-sector spillovers) when promoting cooperative innovation. Based on the evaluation of simulated research collaboration data, sector responses to strategies concerning government intervention in R&D of the firms can now be assessed.
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