Fano Enhancement of Unlocalized Nonlinear Optical Processes

Field localization boosts nonlinear optical processes at the hot spots of metal nanostructures. Fano resonances can further enhance these "local" processes taking place at the hot spots. However, in conventional nonlinear materials, the frequency conversion takes place along the entire crystal body. That is, the conversion process is "unlocalized". The path interference (Fano resonance) schemes developed for localized processes become useless in such materials. Here, we develop Fano enhancement schemes for unlocalized nonlinear optical processes. We show that 3 orders of magnitude Fano enhancement multiply the enhancements achieved via field trapping techniques, e.g., in epsilon-near-zero~(ENZ) materials. We demonstrate the phenomenon both analytically and by numerical solutions of Maxwell's equations. The match between the two solutions is impressive. We observe that the interference scheme for unlocalized processes is richer than the one for the local processes. The method can be employed for any kind of nonlinear optical conversion. Moreover, the Fano enhancement can be continuously controlled by an applied voltage.Comment: 10 pages, 5 figure

Spin Squeezing with Coherent Light via Entanglement Swapping

We analyze theoretically a scheme that produces spin squeezing via the continuous swapping of atom-photon entanglement into atom-atom entanglement, and propose an explicit experimental system where the necessary atom-field coupling can be realized. This scheme is found to be robust against perturbations due to other atom-field coupling channels.Comment: 6 pages, 10 figure

Superradiance induced topological vortex phase in a Bose-Einstein condensate

We investigate theoretically a topological vortex phase transition induced by a superradiant phase transition in an atomic Bose-Einstein condensate driven by a Laguerre-Gaussian optical mode. We show that superradiant radiation can either carry zero angular momentum, or be in a rotating Laguerre-Gaussian mode with angular momentum. The conditions leading to these two regimes are determined in terms of the width for the pump laser and the condensate size for the limiting cases where the recoil energy is both much smaller and larger than the atomic interaction energy.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Quantum entanglement and light propagation through Bose-Einstein condensate (BEC)

Ankara : Bilkent Unıversity, 2009.Thesis (Ph. D.) -- Bilkent University, 2009.Includes bibliographical references leaves 74-80We investigate the optical response of coherent media, a Bose-Einstein condensate (BEC), to intense laser pump stimulations and weak probe pulse propagation. First, we adopt the coherence in sequential superradiance (SR) as a tool for continuous-variable (CV) quantum entanglement of two counter-propagating pulses from the two end-fire modes. In the first-sequence the end-fire and side mode are CV entangled. In the second sequence of SR, this entanglement is swapped in between the two opposite end-fire modes. Second, we investigate the photonic bands of an atomic BEC with a triangular vortex lattice. Index contrast between the vortex cores and the bulk of the condensate is achieved through the enhancement of the index via atomic coherence. Frequency dependent dielectric function is used in the calculations of the bands. We adopt a Poynting vector method to distinguish the photonic band gaps from absorption/gain regimes.Taşgın, Mehmet EmrePh.D

Photonic Band Gap in the Triangular Lattice of BEC vortices

We investigate the photonic bands of an atomic Bose-Einstein condensate with a triangular vortex lattice. Index contrast between the vortex cores and the bulk of the condensate is achieved through the enhancement of the index via atomic coherence. Frequency dependent dielectric function is used in the calculations of the bands, resulting in photonic band gap widths of a few MHz.Comment: 8 pages, 6 figure

Investigation of multiple ıntelligence areas of vocational school students of higher education

Bu çalışmada üniversite öğrencilerinin çoklu zekâ alanlarının çeşitli değişkenler açısından incelenmesi amaçlanmıştır. Nicel araştırma yöntemlerinden tarama modelinin kullanıldığı bu çalışmanın evrenini bir devlet üniversitesinin meslek yüksekokulunda 2017 - 2018 eğitim - öğretim yılı bahar yarıyılında öğrenim gören öğrenciler oluşturmaktadır. Örneklemi ise ilgili evrenden basit seçkisiz örnekleme yöntemi ile belirlenen 260 öğrenci oluşturmaktadır. Veri toplama aracı olarak “Kişisel Bilgi Formu” ve Armstrong (1993) tarafından geliştirilen ve Saban (2002) tarafından düzenlenen “Çoklu Zekâ Alanları Envanteri” kullanılmıştır. Normallik varsayımlarının karşılanıp karşılanmadığına ilişkin yapılan analizler sonucunda verilerin normal dağılmadığı belirlenmiştir. Verilerin analizinde parametrik olmayan testlerden, Mann Whitney U testi ile Kruskal Wallis testi kullanılmıştır. Çalışmada öğrencilerin Çoklu Zekâ Alanları Envanteri’ne verdikleri cevaplar değerlendirilmiş ve sosyal zeka seviyelerinin yüksek olduğu, diğer zeka seviyelerinin ise düşük olduğu sonucuna ulaşılmıştır. Ayrıca araştırma sonucunda öğrencilerin cinsiyetleri ile çoklu zeka alanları arasında anlamlı farklılığa rastlanmazken, öğretim türleri ve bölümleri ile çoklu zeka alanları arasında istatistiksel olarak anlamlı farklılıklara rastlanmıştır.In this study, it has been aimed to examine the multiple intelligence areas of vocational school students in terms of various variables. The target population of this study in which the survey model, one of the quantitative research methods has been used constitutes the students who receive education in the vocational schools of a state university during spring semester of 2017-2018 academic year. The sample is composed of 260 students determined by simple random sampling method from the related target population. As data collection tool, "Personal Information Form" and "Multiple Intelligence Areas Inventory" that was developed by Armstrong (1993) and organized by Saban (2002) have been used. As a result of the normality analyses, it has been determined that the data are not normally distributed. Thus, Mann Whitney U test and Kruskal Wallis test which are not among the parametric tests have been used in the data analyses. In the study, the answers given by the students to the Multiple Intelligence Areas Inventory were evaluated and the results indicated that students’ interpersonal intelligence levels were found high and the other intelligence levels were low. In addition to this, while the results of the study did not reveal any significant differences between the genders of students and multiple intelligence areas, statistically significant differences were found between the types of education, departments and multiple intelligence areas

Testing the reliability of a velocity definition in dispersive medium

We introduce a method to test if a given velocity definition corresponds to an actual physical flow, when the pulse propagation in dispersive medium is considered. i) We calculate the mean arrival time between two positions in space, using the Fourier expansion in real-\omega space. ii) We calculate the mean spatial displacement between two points in time, using the Fourier expansion in real-k space. We compare the velocities calculated in the two approaches. If the velocity definition truly corresponds to an actual flow, the two velocities must be the same. However, we show that the two velocities differ significantly (4%) in the region of superluminal propagation even for the successful definition introduced by Peatross et al. [Phys. Rev. Lett. 84, 2370 (2000)].Comment: 5 pages, 3 figure

A Simple Nonviral Method to Generate Human Induced Pluripotent Stem Cells Using SMAR DNA Vectors

Induced pluripotent stem cells (iPSCs) are a powerful tool for biomedical research, but their production presents challenges and safety concerns. Yamanaka and Takahashi revolutionised the field by demonstrating that somatic cells could be reprogrammed into pluripotent cells by overexpressing four key factors for a sufficient time. iPSCs are typically generated using viruses or virus-based methods, which have drawbacks such as vector persistence, risk of insertional mutagenesis, and oncogenesis. The application of less harmful nonviral vectors is limited as conventional plasmids cannot deliver the levels or duration of the factors necessary from a single transfection. Hence, plasmids that are most often used for reprogramming employ the potentially oncogenic Epstein–Barr nuclear antigen 1 (EBNA-1) system to ensure adequate levels and persistence of expression. In this study, we explored the use of nonviral SMAR DNA vectors to reprogram human fibroblasts into iPSCs. We show for the first time that iPSCs can be generated using nonviral plasmids without the use of EBNA-1 and that these DNA vectors can provide sufficient expression to induce pluripotency. We describe an optimised reprogramming protocol using these vectors that can produce high-quality iPSCs with comparable pluripotency and cellular function to those generated with viruses or EBNA-1 vectors.</p

1991-2015 arası Türk-Rus ekonomik ilişkileri ve bu ilişkilerde müteahhitlik sektörünün rolü

ÖZETTürk - Rus ilişkileri, geçmişi birkaç yüzyıla dayanan ve her dönemin kendi içerisinde özel bir değerlendirmeye ihtiyacı olan bir tarihe sahiptir. 20.yüzyıla kadar savaşlarla geçen bu ilişkiler 1917 Ekim Devriminden sonra daha farklı bir boyuta evirilmiştir. Batı Emperyalizmine karşı bir politik temeli olan bu yeni Rus Rejimi yine Batı’ya karşı mücadele veren yeni Türk Hükümetini desteklemiş ve uzun yıllar sonra uluslararası ilişkilerde bu denli yakın ilişkiler kurulmuştur. Soğuk Savaş döneminde ise uluslararası ilişkiler sisteminin iki farklı kutbunda bulunan Türkiye ve Rusya buna rağmen ikili ilişkilerini sürdürmüşlerdir. 80li yılların ortalarından itibaren de ekonomik ilişkiler daha yakın bir hal almıştır. Buradaki en önemli dönüm noktası 1984 yılında imzalanan “Doğalgaz Alımı Antlaşması”dır. Bu anlaşma ile Türkiye-Rusya ilişkileri ekonomik ilişkiler anlamında yeni bir boyut kazanmıştır. Bu çalışmada, tarihsel olarak Türk-Rus ilişkileri siyasi, ekonomik ve sosyal bir çerçevede ele alınmıştır. Disiplinler arası bir bakış açısı ile bu ilişkilerin birbiri ile olan ilişkileri üzerine durulmuş ve siyasi ve ekonomik gelişmelerin birbirinden ayırılmadan ele alınması gerekliliği üzerine odaklanılmıştır. Çalışmayı diğer çalışmalardan ayıran en belirgin özellikte konuyu salt enerji, ekonomi veya siyasi ilişkilerin üzerinden değil, bunları bir bütün olarak ele almasıdır. Bulgularda daha önce yapılmış araştırmalardan elde edilen sonuçlardan yararlanılmış ve daha önce yapılan çalışmalarda çoğunlukla üzerinde durulan enerji ve turizm alanındaki ilişkilerin yanı sıra önemli bir ekonomik tarihe ve yapıya sahip olan taahhüt sektörü üzerine bir çalışma yürütülmüştür. Müteahhitlik sektörünün de hem istihdam hem de ekonomik getiri olarak enerji ve turizm alanları kadar önemli olduğu ve özellikle yurt dışı istihdam ile yumuşak güç kavramı üzerinden uluslararası ilişkiler açısından önemli olabilecek bir alan olduğu kavramı benimsenmiştir.ABSTRACTTurkish-Russian relations have a background of centuries and every period has the importance that requires to be examined individually. The relations were under the strain of war until the 20th century then developed another dimension following the 1917 Revolution. The new Russian regime, which was politically against Western Imperialism, supported the Turkish Government who also was at war with the West. After decades the two governments initiated very close relations. In this study, the history of Turkish-Russian relations are examined in political, economical and social aspects. With an inter-disciplinary point of view, these relations are examined in regard to their interactions with each other and focused on the necessity of discussing the political and economic indissociably. What makes this study unique is its aim to examine the subject, not discussing economics and politics individually but as a whole. In findings, this study benefited from the outcomes of previous research and the extent of this study is taken beyond the relations in energy and tourism sectors the construction sector which has significance in terms of the context and economic history. This study refers to the contraction business as equally important as energy and tourism sectors in terms of economy and employment. Especially its importance in employment abroad and in the international relations arena as a soft power concept