Fabrication of quantum emitters in aluminium nitride by Al-ion implantation and thermal annealing

Single-photon emitters (SPEs) within wide-bandgap materials represent an appealing platform for the development of single-photon sources operating at room temperatures. Group III- nitrides have previously been shown to host efficient SPEs which are attributed to deep energy levels within the large bandgap of the material, in a way that is similar to extensively investigated colour centres in diamond. Anti-bunched emission from defect centres within gallium nitride (GaN) and aluminium nitride (AlN) have been recently demonstrated. While such emitters are particularly interesting due to the compatibility of III-nitrides with cleanroom processes, the nature of such defects and the optimal conditions for forming them are not fully understood. Here, we investigate Al implantation on a commercial AlN epilayer through subsequent steps of thermal annealing and confocal microscopy measurements. We observe a fluence-dependent increase in the density of the emitters, resulting in creation of ensembles at the maximum implantation fluence. Annealing at 600 {\deg}C results in the optimal yield in SPEs formation at the maximum fluence, while a significant reduction in SPE density is observed at lower fluences. These findings suggest that the mechanism of vacancy formation plays a key role in the creation of the emitters, and open new perspectives in the defect engineering of SPEs in solid state.Comment: 11 pages, 7 figure

Evanescent-field assisted photon collection from quantum emitters under a solid immersion lens

Solid-state quantum light sources are being intensively investigated for applications in quantum technology. A key challenge is to extract light from host materials with high refractive index, where efficiency is limited by refraction and total internal reflection. Here we show that an index-matched solid immersion lens can, if placed sufficiently close to the semiconductor, extract light coupled through the evanescent field at the surface. Using both numerical simulations and experiments, we investigate how changing the thickness of the spacer between the semiconductor and lens impacts the collection efficiency (CE). Using automatic selection and measurement of 100 s of individually addressable colour centres in several aluminium nitride samples we demonstrate spacer-thickness dependent photon CE enhancement, with a mean enhancement factor of 4.2 and a highest measured photon detection rate of 743±4kcps

The Offshoring of Production Activities in European Manufacturing

We investigate production offshoring – the relocation of production activities to locations abroad – of European firms. The analysis employs data from the European Manufacturing Survey (EMS). Offshoring activity is declining across most countries, sectors, and firm sizes between the periods 2004/06 and 2007/09. Regression analysis reveals that this decline is also significant after controlling for firm characteristics. Long-term data for Germany indicate that this decrease is part of a longer trend which already started in 2003. Despite the general decrease in offshoring, far-shoring to Asia in general and to China in particular has increased. In contrast, near-shoring to EU member states in Middle and Eastern Europe (EU-12) became less attractive. The EU-12, however, is still the most important target region for offshoring activities of European firms. The dominant motive for offshoring is the wish to reduce labour costs. Expected labour cost reductions explain offshoring to the EU-12, Asia and China in particular. Vicinity to customers and market expansion follow as a motive with a wide margin. However, in contrast to the EU-12, where the offshoring decision is solely dominated by potential labour cost savings, offshoring activities to Asia and China are also significantly related to market expansion motives

Post-Covid-19 Irritable Bowel Syndrome

Objectives The long-term consequences of COVID-19 infection on the gastrointestinal tract remain unclear. Here, we aimed to evaluate the prevalence of gastrointestinal symptoms and post-COVID-19 disorders of gut-brain interaction after hospitalisation for SARS-CoV-2 infection. Design GI-COVID-19 is a prospective, multicentre, controlled study. Patients with and without COVID-19 diagnosis were evaluated on hospital admission and after 1, 6 and 12 months post hospitalisation. Gastrointestinal symptoms, anxiety and depression were assessed using validated questionnaires. Results The study included 2183 hospitalised patients. The primary analysis included a total of 883 patients (614 patients with COVID-19 and 269 controls) due to the exclusion of patients with pre-existing gastrointestinal symptoms and/or surgery. At enrolment, gastrointestinal symptoms were more frequent among patients with COVID-19 than in the control group (59.3% vs 39.7%, p < 0.001). At the 12-month follow-up, constipation and hard stools were significantly more prevalent in controls than in patients with COVID-19 (16% vs 9.6%, p=0.019 and 17.7% vs 10.9%, p=0.011, respectively). Compared with controls, patients with COVID-19 reported higher rates of irritable bowel syndrome (IBS) according to Rome IV criteria: 0.5% versus 3.2%, p=0.045. Factors significantly associated with IBS diagnosis included history of allergies, chronic intake of proton pump inhibitors and presence of dyspnoea. At the 6-month follow-up, the rate of patients with COVID-19 fulfilling the criteria for depression was higher than among controls. Conclusion Compared with controls, hospitalised patients with COVID-19 had fewer problems of constipation and hard stools at 12 months after acute infection. Patients with COVID-19 had significantly higher rates of IBS than controls

Data Descriptor : A European Multi Lake Survey dataset of environmental variables, phytoplankton pigments and cyanotoxins

Under ongoing climate change and increasing anthropogenic activity, which continuously challenge ecosystem resilience, an in-depth understanding of ecological processes is urgently needed. Lakes, as providers of numerous ecosystem services, face multiple stressors that threaten their functioning. Harmful cyanobacterial blooms are a persistent problem resulting from nutrient pollution and climate-change induced stressors, like poor transparency, increased water temperature and enhanced stratification. Consistency in data collection and analysis methods is necessary to achieve fully comparable datasets and for statistical validity, avoiding issues linked to disparate data sources. The European Multi Lake Survey (EMLS) in summer 2015 was an initiative among scientists from 27 countries to collect and analyse lake physical, chemical and biological variables in a fully standardized manner. This database includes in-situ lake variables along with nutrient, pigment and cyanotoxin data of 369 lakes in Europe, which were centrally analysed in dedicated laboratories. Publishing the EMLS methods and dataset might inspire similar initiatives to study across large geographic areas that will contribute to better understanding lake responses in a changing environment.Peer reviewe

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature

The Conservation Project Of The Wooden Houses Situated In Eyüp District Islambey Quarter 217 Block 65 Parcel

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Bu çalışmada Eyüp İslambey Mahallesi, İslambey Çeşmesi Sokak 217 Ada 65 Parsel’de yer alan ahşap konutlar konu alınmıştır. Yapıların içinde yer aldığı Eyüp İlçesi, ilk Osmanlı sur dışı yerleşim bölgesidir. Aynı zamanda Osmanlı-Türk şehirciliğinin tipik bir örneği olan Eyüp’te sayıları giderek azalmakta olan özgün ahşap sivil mimarlık örneklerinin araştırılması Türk konut tipinin gelecek nesillere aktarılması açısından da büyük önem taşıması sebebiyle, söz konusu ahşap yapılar tez konusu olarak seçilmiştir. İslambey Çeşmesi Sokağı ile Bahçeli Çeşme Çıkmazı Sokağı’nın kesişimindeki köşe parselde yer alan iki ahşap yapı birbirine bitişik tasarlanmıştır ve aynı bahçeyi kullanmaktadır. Yapıların kesin inşa tarihi bilinmemekle birlikte farklı zamanlarda yapıldığı düşünülmektedir. Elde edilen verilerden yapıların 19. Yüzyıl sonlarında inşa edildiği sanılmaktadır. Özgün ahşap detayların büyük ölçüde korunduğu yapılar, 1960’lı yılların sonlarında üç farklı ailenin birbirinden bağımsız olarak aynı parseli kullanabileceği şekilde bölümlendirilmiştir.Tez çalışmasının birinci bölümünde amaç ve yöntemler belirlenmiş, ikinci bölümde çalışma arazisinin bulunduğu Eyüp İlçesi ve yapıların yakın çevresi kısaca tanıtılmış, üçüncü bölümde yapının mevcut durumu detaylıca anlatılarak malzeme ve bozulma tespitleri yapılmıştır. Dördüncü bölümde, çeşitli bilgiler ışığında restitüsyon projeleri geliştirilmiş, daha sonraki bölümde yapının ihtiyaç duyduğu müdahale önerileri yapılmış ve son olarak da genel bir değerlendirmenin yapıldığı sonuç bölümü yazılmıştır.In this research the wooden houses situated in Eyüp Islambey Quarter, Islambey Çeşmesi Street, 217 Block 65 Parcel are studied. The surveyed site is located in Eyüp district, the first Ottoman residential zone ever to be situated outside of the city walls. A typical model of the traditional Ottoman-Turkish urbanism, Eyüp district embodies unique examples of timber structured civil architecture. Undertaking a detailed survey of this site, therefore, constitutes great importance for the documention of Turkish housing archetypes and generating a reliable archive for the next generations. The two timber houses situated at the intersection parcel of İslam Bey Çeşmesi Street and Bahçeli Çeşme Çıkmazı Street are constructed adjacently and they inhabit the same garden. Although the accurate construction dates remain unknown, it is estimated that the two dwellings were built in different dates. According to the obtained information, the buildings were finished about the late 19th century. In 1970s, the structures were fragmented in way that enabled the independent utilization of the same parcel by three different families. Specifications on the aim and method of the research are clarified in the first part of the thesis, while the information on Eyüp district and surroundings is included in the second part. In the third part, an analysis of the present condition is realized and the information on materials and deteriorations are documented. The fourth part includes a restitution project that is constituted in light of the corresponding findings, while the required interventions for the analyzed structures are proposed in the next part. Finally, the epilogue consists of an overall evaluation of the research.Yüksek LisansM.Sc

Fullerene-Attached Polymeric Homogeneous/Heterogeneous Photoactivators for Visible-Light-Induced CuAAC Click Reactions

In this work, a visible-light -inducedcopper(I)-catalyzed azide alkyne cycloaddition (CuAAC) dick reaction via an electron transfer reaction employing fullerene (C-60) containing linear polystyrene and network polymer as homogeneous and heterogeneous activators, PS-C-60 and Gel-C-60, respectively, is described. Various low molar mass organic and polymeric azide and alkyne compounds are used to conduct the click reaction, and almost quantitative yields are attained. Compared to the bare C-60, the polymers with C-60, units exhibited a much higher promoting effect to catalyze CuAAC reactions