Resolving the emission transition dipole moments of single doubly-excited seeded nanorods via heralded defocused imaging

Semiconductor nanocrystal emission polarization is a crucial probe of nanocrystal physics and an essential factor for nanocrystal-based technologies. While the transition dipole moment of the lowest excited state to ground state transition is well characterized, the dipole moment of higher multiexcitonic transitions is inaccessible via most spectroscopy techniques. Here, we realize direct characterization of the doubly-excited state relaxation transition dipole by heralded defocused imaging. Defocused imaging maps the dipole emission pattern onto a fast single-photon avalanche diode detector array, allowing the post-selection of photon pairs emitted from the biexciton-exciton emission cascade and resolving the differences in transition dipole moments. Type-I1/2 seeded nanorods exhibit higher anisotropy of the biexciton-to-exciton transition compared to the exciton-to-ground state transition. In contrast, type-II seeded nanorods display a reduction of biexciton emission anisotropy. These findings are rationalized in terms of an interplay between transient dynamics of the refractive index and the excitonic fine structure

Экспериментальная автоматизированная система гидрометеорологических измерений и обработки данных для береговых станций

Разработан действующий макет автоматизированной системы прибрежных гидрометеорологических измерений для морской сети Госгидромета Украины. В течение 2000 – 2004 гг. проведены испытания и опытная эксплуатация метеорологических (ветер, температура воздуха, атмосферное давление) и гидрологических (уровень, температура и соленость воды) измерительных блоков, установленных в стандартных условиях морской станции «Севастополь». Приводятся данные о структуре, основных технологических принципах автоматизированной системы и некоторые результаты квазинепрерывных метеорологических и гидрологических измерений.Developed is functioning model of automated system of coastal hydrometeorological measurements for the marine net of State Hydrometeorological Institution of Ukraine. In 2000 – 2004 the tests and experimental exploitation of meteorological (wind, atmospheric temperature, atmospheric pressure) and hydrological (water level, temperature and salinity) measuring blocks installed in standard conditions of marine station “Sevastopol” were held. Data on structure, general technological principles of the automated system and some results of quazi-continuous meteorological and hydrological measurements is presented

Метод трехмерной триангуляции в задачах кластерного анализа

Представлен метод многомерного шкалирования на основе трехмерной триангуляции. Рассмотрена возможность качественного сохранения геометрической структуры множества объектов при отображении многомерного пространства в трехмерное. Приведены результаты применения метода для решения задачи кластеризации на примере периодической системы элементов Д.И. Менделеева. Экспериментально показано, что по критериям качества кластеризации предложенный метод более эффективен в сравнении с методами k-средних и нейронной сети Кохонена.Представлено метод багатовимірного шкалювання на основі тривимірної тріангуляції. Розглянуто можливість якісного збереження геометричної структури множини об’єктів при відображенні багатовимірного простору в тривимірне. Наведено результати застосування методу для вирішення задачі кластеризації на прикладі періодичної системи елементів Д.І. Менделєєва. Експериментально показано, що за критеріями якості кластеризації запропонований метод більш ефективний у порівнянні з методами k-середніх та нейронної мережі Кохонена.The method of multidimensional scaling on the basis of the 3-D triangulation is presented. The qualitative preservation possibility of geometrical structure of objects by multidimensional space mapping to three- dimensional space is considered. The results of application of the method for clustering problem of the Mendeleyev periodic table are presented. It is experimentally shown, that the presented method is more effective by criteria of clustering quality in comparison with the methods of k-averages and the Kohonen neural network

Impact of Noise and Background on Measurement Uncertainties in Luminescence Thermometry

Materials with temperature-dependent luminescence can be used as local thermometers when incorporated in, for example, a biological environment or chemical reactor. Researchers have continuously developed new materials aiming for the highest sensitivity of luminescence to temperature. Although the comparison of luminescent materials based on their temperature sensitivity is convenient, this parameter gives an incomplete description of the potential performance of the materials in applications. Here, we demonstrate how the precision of a temperature measurement with luminescent nanocrystals depends not only on the temperature sensitivity of the nanocrystals but also on their luminescence strength compared to measurement noise and background signal. After first determining the noise characteristics of our instrumentation, we show how the uncertainty of a temperature measurement can be predicted quantitatively. Our predictions match the temperature uncertainties that we extract from repeated measurements, over a wide temperature range (303-473 K), for different CCD readout settings, and for different background levels. The work presented here is the first study that incorporates all of these practical issues to accurately calculate the uncertainty of luminescent nanothermometers. This method will be important for the optimization and development of luminescent nanothermometers

Dual-Wavelength Lasing in Quantum-Dot Plasmonic Lattice Lasers

Arrays of metallic particles patterned on a substrate have emerged as a promising design for on-chip plasmonic lasers. In past examples of such devices, the periodic particles provided feedback at a single resonance wavelength, and organic dye molecules were used as the gain material. Here, we introduce a flexible template-based fabrication method that allows a broader design space for Ag particle-array lasers. Instead of dye molecules, we integrate colloidal quantum dots (QDs), which offer better photostability and wavelength tunability. Our fabrication approach also allows us to easily adjust the refractive index of the substrate and the QD-film thickness. Exploiting these capabilities, we demonstrate not only single-wavelength lasing but dual-wavelength lasing via two distinct strategies. First, by using particle arrays with rectangular lattice symmetries, we obtain feedback from two orthogonal directions. The two output wavelengths from this laser can be selected individually using a linear polarizer. Second, by adjusting the QD-film thickness, we use higher-order transverse waveguide modes in the QD film to obtain dual-wavelength lasing at normal and off-normal angles from a symmetric square array. We thus show that our approach offers various design possibilities to tune the laser output

Antiviral responses are shaped by heterogeneity in viral replication dynamics

Antiviral signalling, which can be activated in host cells upon virus infection, restricts virus replication and communicates infection status to neighbouring cells. The antiviral response is heterogeneous, both quantitatively (efficiency of response activation) and qualitatively (transcribed antiviral gene set). To investigate the basis of this heterogeneity, we combined Virus Infection Real-time IMaging (VIRIM), a live-cell single-molecule imaging method, with real-time readouts of the dsRNA sensing pathway to analyse the response of human cells to encephalomyocarditis virus (EMCV) infection. We find that cell-to-cell heterogeneity in viral replication rates early in infection affect the efficiency of antiviral response activation, with lower replication rates leading to more antiviral response activation. Furthermore, we show that qualitatively distinct antiviral responses can be linked to the strength of the antiviral signalling pathway. Our analyses identify variation in early viral replication rates as an important parameter contributing to heterogeneity in antiviral response activation

Fluorescent-Probe Characterization for Pore-Space Mapping with Single-Particle Tracking

Porous solids often contain complex pore networks with pores of various sizes. Tracking individual fluorescent probes as they diffuse through porous materials can be used to characterize pore networks at tens of nanometers resolution. However, understanding the motion behavior of fluorescent probes in confinement is crucial to reliably derive pore network properties. Here, we introduce well-defined lithography-made model pores developed to study probe behavior in confinement. We investigated the influence of probe-host interactions on diffusion and trapping of confined single-emitter quantum-dot probes. Using the pH-responsiveness of the probes, we were able to largely suppress trapping at the pore walls. This enabled us to define experimental conditions for mapping of the accessible pore space of a one-dimensional pore array as well as a real-life polymerization-catalyst-support particle