Quantum-dot-spin single-photon interface

Using background-free detection of spin-state-dependent resonance fluorescence from a single-electron charged quantum dot with an efficiency of 0:1%, we realize a single spin-photon interface where the detection of a scattered photon with 300 picosecond time resolution projects the quantum dot spin to a definite spin eigenstate with fidelity exceeding 99%. The bunching of resonantly scattered photons reveals information about electron spin dynamics. High-fidelity fast spin-state initialization heralded by a single photon enables the realization of quantum information processing tasks such as non-deterministic distant spin entanglement. Given that we could suppress the measurement back-action to well below the natural spin-flip rate, realization of a quantum non-demolition measurement of a single spin could be achieved by increasing the fluorescence collection efficiency by a factor exceeding 20 using a photonic nanostructure

Integrated Lax Formalism for PCM

By solving the first-order algebraic field equations which arise in the dual formulation of the D=2 principal chiral model (PCM) we construct an integrated Lax formalism built explicitly on the dual fields of the model rather than the currents. The Lagrangian of the dual scalar field theory is also constructed. Furthermore we present the first-order PDE system for an exponential parametrization of the solutions and discuss the Frobenious integrability of this system.Comment: 24 page

Phase diagrams of Kitaev models for arbitrary magnetic field orientations

The Kitaev model is an exactly solvable quantum spin model within the language of constrained real fermions. In spite of numerous studies for magnetic fields along special orientations, there is a limited amount of knowledge on the complete field-angle characterization, which can provide valuable information on the existence of fractionalized excitations. For this purpose, we first study the pure ferromagnetic and antiferromagnetic Kitaev models for arbitrary external magnetic field directions via a mean-field theory, showing that there are many topological phases with different (or zero) Chern numbers, depending on the magnetic field strength and orientations. However, a realistic description of the candidate Kitaev materials, within the edge-sharing octahedra paradigm, requires additional coupling terms, including a large off-diagonal term Γ along with possible anisotropic corrections Γp. It is therefore not sufficient to rely on the topological properties of the bare Kitaev model as the basis for the observed thermal Hall-conductivity signals, and an understanding of these extended Kitaev models with a complete field response is demanded. Starting from the zero-field phase diagram of K−Γ−Γp models, we identify, besides the Kitaev spin liquid phase, antiferromagnetic zigzag, ferromagnetic phases, as well as an unusual Kitaev(-Γ) spin liquid phase. The magnetic field response of these phases for arbitrary field orientations provides a remarkably rich phase diagram. For an extended parameter range and just above the critical field where the zigzag phase is suppressed, there is an intermediate phase region with suppressed energy gaps and substantial spin fractionalization. To comply our findings with experiments, we also reproduce a large asymmetry in the extent of this intermediate phases specifically for the two different field directions θ=±60o with respect to the normal to the plane of the honeycomb lattice

Identification of the Retrofit Actions to Achieve Cost-Optimal and NZEB Levels for Residential Buildings in Istanbul Considering the Remaining Building Lifetime

Cost-optimal and nearly-zero energy building (NZEB) levels are two interrelated concepts identified for upgrading energy performance of buildings in Europe. In parallel, many research activities on retrofitting existing buildings in Turkey follow the methodology framework introduced by the European Commission. However, in Turkey, there is a process called "urban transformation" due to the earthquake risk, but the practice is based on new construction after demolishment of existing buildings. Especially in Istanbul, this process has been conducted rapidly. This specific aspect requires assessment of cost-optimal retrofit analyses considering the remaining lifespan of analysed buildings. This study presents a cost-optimality assessment method for retrofitting towards NZEB in Turkey. The method integrates payback period and investment cost assessment to the methodology in order to obtain whole picture for retrofit alternatives. In the paper, suggested method is applied to a reference residential building in Istanbul. After the initial cost-optimal analyses, payback periods and initial investment costs for selected retrofit packages are assessed considering the future lifespan of the building. Together with these, possible subsidy opportunities are also investigated. Results show that, if the expected future lifespan is higher than 10 years, retrofit actions achieving 56.2kWh/m2y primary energy consumption level are considerable. Subsidies are beneficial to obtain reasonable initial investment costs

Effect of Economic Indicators on Cost-Optimal Energy Performance Levels of Residential Buildings Retrofits in the Mediterranean Region of Turkey

This study aims to analyse the effect of economic indicators on cost-optimal levels of residential building retrofits in Mediterranean region of Turkey. Sensitivity analyses were applied on the cost-optimality calculation results for the residential reference building. The sensitivity analyses address discount rate and potential investment cost decreases. Results reveal that 6% variation in the discount rate corresponds to more than 30 kWh/m2y difference in the primary energy consumption of the cost-optimal solutions. Potential investment cost decreases for certain retrofit measures are also effective on identified cost-optimal levels and subsidy opportunities appear as an effective tool to achieve higher energy efficiency in existing buildings and to stimulate building energy retrofits

Identification of the Retrofit Actions to Achieve Cost-Optimal and NZEB Levels for Residential Buildings in Istanbul Considering the Remaining Building Lifetime

Cost-optimal and nearly-zero energy building (NZEB) levels are two interrelated concepts identified for upgrading energy performance of buildings in Europe. In parallel, many research activities on retrofitting existing buildings in Turkey follow the methodology framework introduced by the European Commission. However, in Turkey, there is a process called “urban transformation” due to the earthquake risk, but the practice is based on new construction after demolishment of existing buildings. Especially in Istanbul, this process has been conducted rapidly. This specific aspect requires assessment of cost-optimal retrofit analyses considering the remaining lifespan of analysed buildings. This study presents a cost-optimality assessment method for retrofitting towards NZEB in Turkey. The method integrates payback period and investment cost assessment to the methodology in order to obtain whole picture for retrofit alternatives. In the paper, suggested method is applied to a reference residential building in Istanbul. After the initial cost-optimal analyses, payback periods and initial investment costs for selected retrofit packages are assessed considering the future lifespan of the building. Together with these, possible subsidy opportunities are also investigated. Results show that, if the expected future lifespan is higher than 10 years, retrofit actions achieving 56.2kWh/m2y primary energy consumption level are considerable. Subsidies are beneficial to obtain reasonable initial investment costs

Pathways of bond topology transitions at the interface of silicon nanocrystals and amorphous silica matrix

The interface chemistry of silicon nanocrystals (NCs) embedded in amorphous oxide matrix is studied through molecular dynamics simulations with the chemical environment described by the reactive force field model. Our results indicate that the Si NC-oxide interface is more involved than the previously proposed schemes which were based on solely simple bridge or double bonds. We identify different types of three-coordinated oxygen complexes, previously not noted. The abundance and the charge distribution of each oxygen complex is determined as a function of the NC size as well as the transitions among them. The oxidation at the surface of NC induces tensile strain to Si-Si bonds which become significant only around the interface, while the inner core remains unstrained. Unlike many earlier reports on the interface structure, we do not observe any double bonds. Furthermore, our simulations and analysis reveal that the interface bond topology evolves among different oxygen bridges through these three-coordinated oxygen complexes.Comment: 5 pages 6 figures 1 tabl

Analysis of Strain Fields in Silicon Nanocrystals

Strain has a crucial effect on the optical and electronic properties of nanostructures. We calculate the atomistic strain distribution in silicon nanocrystals up to a diameter of 3.2 nm embedded in an amorphous silicon dioxide matrix. A seemingly conflicting picture arises when the strain field is expressed in terms of bond lengths versus volumetric strain. The strain profile in either case shows uniform behavior in the core, however it becomes nonuniform within 2-3 \AA distance to the nanocrystal surface: tensile for bond lengths whereas compressive for volumetric strain. We reconsile their coexistence by an atomistic strain analysis.Comment: Published in Applied Physics Letters Vol. 94, 191914 (2009

Numerical analysis of the thermal and thermodynamic performance of a parabolic trough solar collector using SWCNTs-Therminol®VP-1 nanofluid

In this paper, energetic and exergetic performances of a parabolic trough solar collector using single-walled carbon nanotubes (SWCNTs)-Therminol® VP-1 nanofluid were numerically investigated and presented. The main objective of this investigation was to determine the influence of high thermal conductivity SWCNTs suspended in the widely used heat transfer fluid, Therminol®VP-1 on the performance indicators of the parabolic trough solar collector. A parabolic trough system with a high concentration ratio of 113 was analyzed in this study. The thermo-physical properties of SWCNTs were taken as functions of nanotube length, nanotube diameter, and temperature, while the properties of Therminol®VP-1 were considered to be temperature dependent. The study involved determination of the actual heat flux profile through Monte Carlo ray tracing and the subsequent coupling of this heat flux profile to a computational fluid dynamics tool using user defined functions. The computational fluid dynamics tool was finite volume based, and the realizable k-ε model together with enhanced wall treatment were used for turbulence modeling. The entropy generation rates were obtained directly from the local velocity and temperature fields of the computed domain and later used in the exergy analysis. Results showed that although the heat transfer performance significantly improved with the use of SWCNTs, the increase in the thermal efficiency was not substantial. For the considered range of parameters, while the heat transfer performance increased up to 234%, the thermal efficiency increased around 4.4% as the volume fraction increased from 0 to 2.5%. The corresponding reduction in the entropy generation was about 70%.This work is based on the research supported in part by the National Research Foundation of South Africa (Grant No. 9927). This support is duly acknowledged and appreciated. Dr. Mwesigye acknowledges the support received from the school of Mechanical, Industrial and Aeronautical Engineering at the University of the Witwatersrand, Dr. Yılmaz acknowledges the support received from the Department of Automotive Engineering at Adana Science and Technology University and Prof. Meyer duly acknowledges the support received from the University of Pretoria.http://www.elsevier.com/locate/renene2019-04-01hj2017Mechanical and Aeronautical Engineerin

The prognostic impact of comorbidity, nutritional and performance status on patients with diffuse large B cell lymphoma

Background: The aim of the study was to investigate the impact of nutritional status, comorbidity, and performance status on patients with diffuse large B-cell lymphoma (DLBCL). Methods: A retrospective study was conducted on 112 DLBCL patients who were diagnosed at our center between 2009 and 2018. Demographic and disease characteristics and laboratory test results were recorded. Assessments were made using the age-adjusted Charlson comorbidity index (CCI-A) for comorbidity, albumin level for nutritional status, and Eastern Cooperative Oncology Group (ECOG) score for performance status. Results: The mean age of the patients was found to be 62.63 ± 15.16 years. The ECOG score of 65 patients (69.1%) was in the range of 0-1. The mean follow-up time of the patients was determined to be 25.24 ± 25.11 months, and at the end of the follow-up period, 64 patients (57.1%) were survivors. The progression-free survival (PFS), overall survival (OS), and 5-year OS rates of those with CCI-A > 4 were found to be significantly lower than those with CCI-A score ≤4 (P < 0.05). As a result of the Cox-Regression (Backward: LR method) analysis, ECOG and albumin levels were found to be independent risk factors for both OS and PFS (P < 0.05). Conclusion: This study demonstrated that CCI-A, ECOG, and nutritional status are independent prognostic markers for DLBCL patients. Initial evaluation of these patients should include all these parameters, which are easily available at the time of diagnosis