Signatures of Bloch-band geometry on excitons: non-hydrogenic spectra in transition metal dichalcogenides

The geometry of electronic bands in a solid can drastically alter single-particle charge and spin transport. We show here that collective optical excitations arising from Coulomb interactions also exhibit unique signatures of Berry curvature and quantum geometric tensor. A non-zero Berry curvature mixes and lifts the degeneracy of $l \neq 0$ states, leading to a time-reversal-symmetric analog of the orbital Zeeman effect. The quantum geometric tensor, on the other hand, leads to $l$-dependent shifts of exciton states that is analogous to the Lamb shift. Our results provide an explanation of the non-hydrogenic exciton spectrum recently calculated for transition metal dichalcogenides. Numerically, we find a Berry curvature induced splitting of $\sim 10$ meV between the $2p_x \pm i2p_y$ states of WSe$_2$.Comment: 5 pages, 2 figure

Demand and Deliver: Refugee Support Organisations in Austria

This article analyses four emerging refugee support organisations in Austria, founded before the so-called refugee crisis in 2015. It argues that these organisations have managed to occupy a middle space between mainstream NGOs and social movements with structures of inclusive governance, a high degree of autonomy, personalised relationships with refugees, and radical critique combined with service delivery. Based on interviews with the founders of each organisation, we show that their previous NGO and social movement experience formed a springboard for the new initiatives. It not only allowed them to identify significant gaps in existing service provision, but also provided the space of confrontation with the asylum system inspiring a strong sense of outrage, which in turn developed into political critique. We argue that this critique combined with identifying the needs of asylum seekers and refugees has produced a new type of organisation, which both delivers services and articulates radical demands. Each organisation offers a space of encounter, which undoes the ‘organised disintegration’ of the asylum system

All-Optical Manipulation of Electron Spins in Carbon-Nanotube Quantum Dots

We demonstrate theoretically that it is possible to manipulate electron or hole spins all optically in semiconducting carbon nanotubes. The scheme that we propose is based on the spin-orbit interaction that was recently measured experimentally; we show that this interaction, together with an external magnetic field, can be used to achieve optical electron-spin state preparation with a fidelity exceeding 99%. Our results also imply that it is possible to implement coherent spin rotation and measurement using laser fields linearly polarized along the nanotube axis, as well as to convert spin qubits into time-bin photonic qubits. We expect that our findings will open up new avenues for exploring spin physics in one-dimensional systems

Ahmed Haşim

Taha Toros Arşivi, Dosya No: 78-Ahmet Haşim. Not: Gazetenin "Denemeler" köşesinde yayımlanmıştır.İstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Growth and characterization of aluminum doped transparent and conductive zinc oxidethin flims

Thesis (Master)--Izmir Institute of Technology, Physics, Izmir, 2010Includes bibliographical references (leaves: 76-81)Text in English; Abstract: Turkish and Englishxiii, 81 leavesThis thesis focuses on fabrication, characterization and understanding physical properties of transparent and conductive Al doped zinc oxide (ZnO) thin films. Films were deposited by magnetron sputtering technique, using separate ZnO and Al targets. SiO2 and glass (microscope slides) were used as substrates. Growths were performed at room temperature in Ar environment at a constant pressure of 3 mTorr. Films were characterized by atomic force microscope, x-ray diffractometer, scanning electron microscope, UV-vis spectroscophotometer and four point probe electrical measurements. Using transmission data, band gaps of the films and using four point probe measurements, resistivities of films were calculated. Firstly properties of pure ZnO films were studied. They were found to be highly transparent; however their resistivity was very high that we could not measure with our instrument. Therefore, ZnO films were uniformly doped with Al. It was seen that decreasing Al content was improving electrical and optical properties. Al concentration of the films was decreased firstly by decreasing deposition power of Al. After that, content was further decreased by depositing stacks of doped and undoped layers (modulation doping). Following that, modulation doped films were deposited with applying RF bias power to substrates. All films were annealed at 300oC for 1 hour in vacuum. The lowest resistivity obtained in this study was 1.68x10-3 .cm. Transmittance and band gap of the corresponding film were 80% and 4.1 eV respectively. The film was fabricated by modulation doping accompanied with substrate bias of 10 W, followed by annealing at 300oC in vacuum

Türkiye’de Eğitim Eşitsizliğini Okumak: İstatistikler ve Coğrafi Dağılımlar

It has now been widely accepted that a university degree is one of the prerequisites of achieving a high social and economic status. In most of the developed countries, a highly educated young generation is considered a path to a long term economic growth and a key factor in the face of a knowledge-based society. In both developed and developing countries, however, academic achievement and the provision of educational services are not distributed equally between different classes, social groups and even different geographies. Turkey is, in many ways, a good example to analyze educational inequalities where education is strongly a class related issue and there has also been a strong dimension of geography as far as the educational provision and performance are considered. The aim of this study is to analyze educational inequalities in Turkey based on school-based differences and district-level geographic distributions. In the article, statistical and spatial methods and the datasets of National University Entrance Examination (LYS), PISA, and Ministry of National Education are used. The main finding of the article is that university graduation as the main indicator of socio-economic status in Turkey is for the most part depends on regional and school-based inequalities. Inequality of opportunity in education makes socio-economic positions distinct and stable and this makes it difficult for the disadvantaged groups, in terms of the geography that they live in and the school types, to break the vicious circle in the long-term. The findings of the article, therefore, indicate how important to build long-term educational policies based on equality of opportunity.Bugün tüm dünyada, bir üniversite derecesinin yüksek bir sosyo-ekonomik statüye ulaşmanın en temel gereklerinden biri olduğu kabul edilmektedir. İyi eğitilmiş genç bir nüfus, pek çok gelişmiş ülke için uzun vadeli kalkınma ve büyümenin temel yolu, küresel ağlarda tutunabilmenin ve ekonomik rekabette yerini kuvvetlendirmenin temel taşı olarak görülmektedir. Buna rağmen, eğitime erişim ve akademik başarı, hem gelişmiş hem de gelişmekte olan ülkelerin pek çoğunda sınıflara, sosyal gruplara, hatta coğrafyaya göre eşit olmayan bir dağılım göstermektedir. Farklılıkların ve eşitsizliklerin coğrafyada belirgin görünümü olan ve son dönemde ekonomik büyümenin ülke politikalarının temelini oluşturduğu Türkiye, bu meselenin sınanması için oldukça iyi bir örnektir. Bu çalışmanın amacı Türkiye’deki eğitim eşitsizliklerini okul temelli ayrımlar ve ilçe düzeyinde coğrafi farklılıklar ve dağılımlar üzerinden analiz etmektir. Çalışmada istatistiksel ve mekansal analiz yöntemleri ile Lisans Yerleştirme Sınav (LYS) sonuçları, PISA ve Milli Eğitim Bakanlığı veri setleri kullanılmıştır. Çalışmanın en önemli bulgusu Türkiye’de sosyo-ekonomik statü ile doğrudan ilişkili olan üniversiteden mezun olma durumunun büyük ölçüde coğrafi ve okul temelli eşitsizliklere bağlı olduğudur. Üniversiteye erişimdeki eşitsizlikler, toplumdaki sosyal ve ekonomik pozisyonları neredeyse değişmez kılmakta ve iyi bir eğitim almada okul türleri ve coğrafya bakımından dezavantajlı olan grupların söz konusu zinciri kırmasını zorlaştırmaktadır. Çalışmanın bulguları ülkede eğitime yönelik uzun vadeli geliştirilebilecek politikaların eğitimde fırsat eşitliği üzerine kurulması gerektiğini göstermiştir

Realization of a cascaded quantum system: heralded absorption of a single photon qubit by a single-electron charged quantum dot

Photonic losses pose a major limitation for implementation of quantum state transfer between nodes of a quantum network. A measurement that heralds successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate heralded absorption of a single photonic qubit generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 meters away. The transfer of quantum information to the spin degree of freedom takes place upon emission of a photon: for a properly chosen or prepared quantum dot, detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node, by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for realization of quantum information protocols based on cascaded quantum systems

Yahya Kemal

Taha Toros Arşivi, Dosya No: 182-Yahya Kemal Beyatlı. Not: Gazetenin "Söyleşi" köşesinde yayımlanmıştır.İstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

20. ölüm yıldönümünde Nurullah Ataç, Nurullah Ataç'ı anlatıyor:Ben

Taha Toros Arşivi, Dosya No: 423-Nurullah-Dr. Galip Ata

Redox regulation of human P53 tumor suppressor gene activity: Identification of redox genes that play role in human P53 reporter gene activity

Thesis (Master)--Izmir Institute of Technology, Molecular Biology and Genetics, Izmir, 2008Includes bibliographical references (leaves: 21-25)Text in English; Abstract: Turkish and Englishviii, 25 leavesThe occurence of p53 gene mutations in many human tumors shows that p53 protein plays an important role in preventing cancers. One of the most important function of p53 protein is its ability to stimulate transcription of other genes that inhibit cell cycle progression and DNA repair mechanisms or apoptosis pathways. p53 gene activity is controlled by a series of mechanisms among which redox regulation has taken little attention. Because of its importance as a tumor suppressor, its role as a cell cycle control protein and transcription factor, we decided to focus on p53 transcriptional activity. Human p53 can be studied in yeast where genetic tools can be used to identify proteins that affect its ability to stimulate transcription of reporter genes. Several studies have shown that the p53 protein is prone to oxidative inactivation. Although yeast does not contain a p53 gene, the similarity of cell cycle control mechanisms and oxidative stress response pathways prompted us to ask whether human p53 was active in yeast cells lacking individual antioxidant genes. In this study, using yeast deletion mutants, p53 reporter gene activity was assayed in different antioxidant mutants that were identified by REDOX-Cys-Search bioinformatic tool by previous studies. Seven antioxidant genes were found to be important in regulating p53 activity. These genes played role in phosphatidylinositol pathway, protein dephosphorylation, cellular iron metabolism, DNA mismatch repair, and three other unknown biochemical pathways.Identification of these new proteins that regulate p53 activity may have broad implications in understanding the complex behaviour of p53 and tumor formation in humans