A Charge and Spin Readout Scheme For Single Self-Assembled Quantum Dots

We propose an all optical spin initialization and readout concept for single self assembled quantum dots and demonstrate its feasibility. Our approach is based on a gateable single dot photodiode structure that can be switched between charge and readout mode. After optical electron generation and storage, we propose to employ a spin-conditional absorption of a circularly polarized light pulse tuned to the single negatively charged exciton transition to convert the spin information of the resident electron to charge occupancy. Switching the device to the charge readout mode then allows us to probe the charge state of the quantum dot (1e, 2e) using non-resonant luminescence. The spin orientation of the resident electron is then reflected by the photoluminescence yield of doubly and singly charged transitions in the quantum dot. To verify the feasibility of this spin readout concept, we have applied time gated photoluminescence to confirm that selective optical charging and efficient non perturbative measurement of the charge state can be performed on the same dot. The results show that, by switching the electric field in the vicinity of the quantum dot, the charging rate can be switched between a regime of efficient electron generation and a readout regime, where the charge occupancy and, therefore, the spin state of the dot can be tested via PL over millisecond timescales, without altering it.Comment: 20 Pages, 6 Figures, submitted to Phys. Rev.

Strong electrically tunable exciton g-factors in an individual quantum dots due to hole orbital angular momentum quenching

Strong electrically tunable exciton g-factors are observed in individual (Ga)InAs self-assembled quantum dots and the microscopic origin of the effect is explained. Realistic eight band k.p simulations quantitatively account for our observations, simultaneously reproducing the exciton transition energy, DC Stark shift, diamagnetic shift and g-factor tunability for model dots with the measured size and a comparatively low In-composition of x(In)~35% near the dot apex. We show that the observed g-factor tunability is dominated by the hole, the electron contributing only weakly. The electric field induced perturbation of the hole wavefunction is shown to impact upon the g-factor via orbital angular momentum quenching, the change of the In:Ga composition inside the envelope function playing only a minor role. Our results provide design rules for growing self-assembled quantum dots for electrical spin manipulation via electrical g-factor modulation

Highly Non-linear Excitonic Zeeman Spin-Splitting in Composition-Engineered Artificial Atoms

Non-linear Zeeman splitting of neutral excitons is observed in composition engineered In(x)Ga(1-x)As self-assembled quantum dots and its microscopic origin is explained. Eight-band k.p simulations, performed using realistic dot parameters extracted from cross-sectional scanning tunneling microscopy, reveal that a quadratic contribution to the Zeeman energy originates from a spin dependent mixing of heavy and light hole orbital states in the dot. The dilute In-composition (x<0.35) and large lateral size (40-50 nm) of the quantum dots investigated is shown to strongly enhance the non-linear excitonic Zeeman gap, providing a blueprint to enhance such magnetic non-linearities via growth engineering

Asymmetric optical nuclear spin pumping in a single uncharged quantum dot

A highly asymmetric dynamic nuclear spin pumping is observed in a single self assembled InGaAs quantum dot subject to resonant optical pumping of the neutral exciton transition leading to a large maximum polarization of 54%. This dynamic nuclear polarization is found to be much stronger following pumping of the higher energy Zeeman state. Time-resolved measurements allow us to directly monitor the buildup of the nuclear spin polarization in real time and to quantitatively study the dynamics of the process. A strong dependence of the observed dynamic nuclear polarization on the applied magnetic field is found, with resonances in the pumping efficiency being observed for particular magnetic fields. We develop a model that fully accounts for the observed behaviour, where the pumping of the nuclear spin system is due to hyperfine-mediated spin flip transitions between the states of the neutral exciton manifold.Comment: published version; 4+ pages, 3 figures (eps

Selective Optical Charge Generation, Storage and Readout in a Single Self Assembled Quantum Dot

We report the investigation of a single quantum dot charge storage device. The device allows selective optical charging of a single dot with electrons, storage of these charges over timescales much longer than microseconds and reliable optical readout of the charge occupancy using a time gated photoluminescence technique. This device enables us to directly investigate the electric field dependent tunneling escape dynamics of electrons at high electric fields over timescales up to 4 us. The results demonstrate that such structures and measurement techniques can be used to investigate charge and spin dynamics in single quantum dots over microsecond timescales.Comment: Accepted for publication in AP

Usage of Biologics on Tomatoes and Peppers

In fruit growing, nowadays a lot of chemical products are used (insecticide, fungicide etc.) in order to protect the plants. However, lately the markets are in need of gardening products which are not treated with pesticide but protected with biologics. In gardening, biological fight against the insects and the diseases is not much maintained because the shares are lower and the gardening products are on a great demand and are very profitable. Due to the great profit of the gardening products, less attention is paid to the biological fight for protection. However, the great environmental pollution evokes great interest in consuming healthy gardening products. Due to the mentioned reasons, lately, fruit producers show interest for usage of biologics to protect the gardening products from some insects and diseases. There appear to be many biologics but the producers of gardening products are not well informed because the interest of usage of biologics is not high. By all means, the market provides verified biologics which show good production results. The great interest in usage of biologics to protect the gardening products from diseases and insects increases, whereas the interest of research institutions to discover better biologics is getting bigger

Monoaminergic Neuropathology in Alzheimer's disease

Acknowledgments This work was supported by The Croatian Science Foundation grant. no. IP-2014-09-9730 (“Tau protein hyperphosphorylation, aggregation, and trans-synaptic transfer in Alzheimer’s disease: cerebrospinal fluid analysis and assessment of potential neuroprotective compounds”) and European Cooperation in Science and Technology (COST) Action CM1103 (“Stucture-based drug design for diagnosis and treatment of neurological diseases: dissecting and modulating complex function in the monoaminergic systems of the brain”). PRH is supported in part by NIH grant P50 AG005138.Peer reviewedPostprin

Regulatory Taking: A Contract Approach

This Article begins by defining the parameters of the fifth amendment\u27s taking clause. The Article then reviews the various tests used in determining whether governmental action constitutes a taking, and discusses the recent Supreme Court decisions within the framework of case law as it has evolved since the Court\u27s 1922 landmark decision, Pennsylvania Coal Co. v. Mahon. Finally, the Article suggests a formula based on well-established contract principles for analyzing the impact of land use regulation on private property interests

Semiautomatic epicardial fat segmentation based on fuzzy c-means clustering and geometric ellipse fitting

Automatic segmentation of particular heart parts plays an important role in recognition tasks, which is utilized for diagnosis and treatment. One particularly important application is segmentation of epicardial fat (surrounds the heart), which is shown by various studies to indicate risk level for developing various cardiovascular diseases as well as to predict progression of certain diseases. Quantification of epicardial fat from CT images requires advance image segmentation methods. The problem of the state-of-the-art methods for epicardial fat segmentation is their high dependency on user interaction, resulting in low reproducibility of studies and time-consuming analysis. We propose in this paper a novel semiautomatic approach for segmentation and quantification of epicardial fat from 3D CT images. Our method is a semisupervised slice-by-slice segmentation approach based on local adaptive morphology and fuzzy c-means clustering. Additionally, we use a geometric ellipse prior to filter out undesired parts of the target cluster. The validation of the proposed methodology shows good correspondence between the segmentation results and the manual segmentation performed by physicians