Rapid detection of porcine circovirus type 4 via multienzyme isothermal rapid amplification

Porcine circovirus type 4 (PCV4) is a newly emerging pathogen that was first detected in 2019 and is associated with diverse clinical signs, including respiratory and gastrointestinal distress, dermatitis and various systemic inflammations. It was necessary to develop a sensitive and specific diagnostic method to detect PCV4 in clinical samples, so in this study, a multienzyme isothermal rapid amplification (MIRA) assay was developed for the rapid detection of PCV4 and evaluated for sensitivity, specificity and applicability. It was used to detect the conserved Cap gene of PCV4, operated at 41°C and completed in 20 min. With the screening of MIRA primer-probe combination, it could detect as low as 101 copies of PCV4 DNA per reaction and was highly specific, with no cross-reaction with other pathogens. Further assessment with clinical samples showed that the developed MIRA assay had good correlation with real-time polymerase chain reaction assay for the detection of PCV4. The developed MIRA assay will be a valuable tool for the detection of the novel PCV4 in clinical samples due to its high sensitivity and specificity, simplicity of operation and short testing time

Assessing the alignment accuracy of state-of-the-art deterministic fabrication methods for single quantum dot devices

The realization of efficient quantum light sources relies on the integration of self-assembled quantum dots (QDs) into photonic nanostructures with high spatial positioning accuracy. In this work, we present a comprehensive investigation of the QD position accuracy, obtained using two marker-based QD positioning techniques, photoluminescence (PL) and cathodoluminescence (CL) imaging, as well as using a marker-free in-situ electron beam lithography (in-situ EBL) technique. We employ four PL imaging configurations with three different image processing approaches and compare them with CL imaging. We fabricate circular mesa structures based on the obtained QD coordinates from both PL and CL image processing to evaluate the final positioning accuracy. This yields final position offset of the QD relative to the mesa center of $\mu_x$ = (-40$\pm$58) nm and $\mu_y$ = (-39$\pm$85) nm with PL imaging and $\mu_x$ = (-39$\pm$30) nm and $\mu_y$ = (25$\pm$77) nm with CL imaging, which are comparable to the offset $\mu_x$ = (20$\pm$40) nm and $\mu_y$ = (-14$\pm$39) nm obtained using the in-situ EBL method. We discuss the possible causes of the observed offsets, which are significantly larger than the QD localization uncertainty obtained from simply imaging the QD light emission from an unstructured wafer. Our study highlights the influences of the image processing technique and the subsequent fabrication process on the final positioning accuracy for a QD placed inside a photonic nanostructure

Symmetric Excitons in an (001)-Based InAs/GaAs Quantum Dot Near Si Dopant for Photon-Pair Entanglement

The sacrificed-QD-layer method can well control the indium deposition amount to grow InAs quantum dots (QDs) with isotropic geometry. Individual Si dopant above an (001)-based InAs QD proves a new method to build a local electric field to reduce fine structure splitting (FSS = X1−X2) and show D3h symmetric excitons. The lowest FSS obtained is 3.9 μeV with the lowest energy X state (LX) anticlockwise rotate from [1–10] (i.e., zero FSS will be crossed in a proper field). The lateral field projection induces a large eh separation and various FSS, LX, and emission intensity polarization. The lateral field along [1–10] breaks the X1–X2 wavefunction degeneracy for independent HH and VV cascade emissions with robust polarization correlation. With FSS ~4 μeV and T1 ~0.3 ns fastened in a distributed Bragg reflector cavity, polarization-resolved XX–X cross-correlations show fidelity ~0.55 to a maximal entangled state |HH> + |VV>. A higher fidelity and zero FSS will be obtained in the hybrid QD structure with a junction field integrated to tune the FSS and a sub-bandgap excitation to avoid influences from electrons in the barrier

Study of quantum dots on solar energy applications

This thesis studies p-i-n GaAs solar cells with self-assembled InAs quantum dots (QDs) inserted. The values of this work lie in three aspects. First, by comparing the cell performance with QDs in the i-region and the n-region, the photocurrent (PC) production from QDs by thermal activation and/or intermediate band (IB) absorption is proved to be much lower in efficiency than tunneling. Second, the efficiency of PC production from QDs, characterized by PC spectrum, is helpful to design QD-based photodetectors. Third, closely spaced InAs QD layers allow a strong inter-layer tunneling, leading to an effective PC production from QD deep states, potential for solar cell application. Fourth, from the temperature-dependent PC spectra the minority photohole thermal escape is found to be dominant on PC production from QDs in the n-region. The thermal activation energy reflects the potential variations formed by electron filling in QDs. Apart from InAs QDs, this thesis also explores the blinking correlation between two colloidal CdSe QDs. For QD distance of 1 µm or less, there is a bunched correlation at delay τ = 0, meaning that the two QDs blink synchronously. Such correlation disappears gradually as QD distance increases. The correlation is possibly caused by the stimulated emission between the two nearby QDs.QC 2012050

Metamorphic Quantum Well Lasers

This chapter provides an overview of long wavelengthmetamorphic quantum well lasers. The idea of metamorphic growth is to compromise large lattice mismatch by utilizing a relaxed buffer layer. Structural design and growth optimization of metamorphic buffer layers are reviewed with emphasis on composition grading scheme and doping effects. Progress on long wavelength (>1.2 μm) metamorphic quantum well lasers is summarized

Metamorphic Quantum Well Lasers

This chapter provides an overview of long wavelengthmetamorphic quantum well lasers. The idea of metamorphic growth is to compromise large lattice mismatch by utilizing a relaxed buffer layer. Structural design and growth optimization of metamorphic buffer layers are reviewed with emphasis on composition grading scheme and doping effects. Progress on long wavelength (>1.2 μm) metamorphic quantum well lasers is summarized