Lensfree on-chip microscopy based on single-plane phase retrieval.

We propose a novel single-plane phase retrieval method to realize high-quality sample reconstruction for lensfree on-chip microscopy. In our method, complex wavefield reconstruction is modeled as a quadratic minimization problem, where total variation and joint denoising regularization are designed to keep a balance of artifact removal and resolution enhancement. In experiment, we built a 3D-printed field-portable platform to validate the imaging performance of our method, where resolution chart, dynamic target, transparent cell, polystyrene beads, and stained tissue sections are employed for the imaging test. Compared to state-of-the-art methods, our method eliminates image degradation and obtains a higher imaging resolution. Different from multi-wavelength or multi-height phase retrieval methods, our method only utilizes a single-frame intensity data record to accomplish high-fidelity reconstruction of different samples, which contributes a simple, robust, and data-efficient solution to design a resource-limited lensfree on-chip microscope. We believe that it will become a useful tool for telemedicine and point-of-care application.

Least-Square-Method-Based Optimal Laser Spots Acquisition and Position in Cooperative Target Measurement.

The relative positioning precisions of coordinate points is an important indicator that affects the final accuracy in the visual measurement system of space cooperative targets. Many factors, such as measurement methods, environmental conditions, data processing principles and equipment parameters, are supposed to influence the cooperative target's acquisition and determine the precision of the cooperative target's position in a ground simulation experiment with laser projected spots on parallel screens. To overcome the precision insufficiencies of cooperative target measurement, the factors of the laser diode supply current and charge couple device (CCD) camera exposure time are studied in this article. On the hypothesis of the optimal experimental conditions, the state equations under the image coordinates' system that describe the laser spot position's variation are established. The novel optimizing method is proposed by taking laser spot position as state variables, diode supply current and exposure time as controllable variables, calculating the optimal controllable variables through intersecting the focal spot centroid line and the 3-D surface, and avoiding the inconvenience of solving nonlinear equations. The experiment based on the new algorithm shows that the optimal solution can guarantee the focal spot's variation range in 5-10 pixels under image coordinates' system equivalent to the space with a 3 m distance and 0.6-1.2 mm positioning accuracy.

Balanced Distribution Adaptation for Metal Oxide Semiconductor Gas Sensor Array Drift Compensation.

Drift compensation is an important issue for metal oxide semiconductor (MOS) gas sensor arrays. General machine learning methods require constant calibration and a large amount of label gas data. At the same time, recalibration will cause a lot of costs, and label gas is difficult to obtain in practice. In this paper, a novel drift compensation method based on balanced distribution adaptation (BDA) is proposed. First, the BDA drift compensation method can adjust the conditional distribution and marginal distribution between the two domains through the weight balance factor, thereby more effectively reducing the mismatch between the two domains. When the BDA method performs classification tasks through machine learning, no labeled data is required in the target domain. Then, the particle swarm optimization algorithm is used to improve the accuracy of drift compensation. Individuals in the population are initialized randomly, and their fitness values are calculated. Iterative optimization of the population individuals is conducted until the optimal weight balance factor parameters are calculated. Finally, the BDA method is experimentally verified on the public gas sensor drift data set. Experimental results showed that the BDA method was significantly better than the existing joint distribution adaptation (JDA) method and other standard drift compensation methods such as K-Nearest Neighbor (KNN). In the two setting groups, the recognition accuracy was 4.54% and 1.62% ahead of the JDA method, and 12.23% and 15.83% ahead of the KNN method.

Strategy to Decrease the Angle Measurement Error Introduced by the Use of Circular Grating in Dynamic Torque Calibration.

A circular grating angle encoder is a key component in the dynamic torque calibration system. To improve the accuracy of an angle measurement, in this paper, the source of the angle measurement error of the circular grating is analyzed; an eccentricity error model and an inclination error model are proposed, respectively; further, these two models are combined to establish a total error model. Through the simulation study with the models, the conditions, in which the eccentricity error or inclination error can be ignored, are discussed. The calibration and compensation methods of the angle measurement error are given, and a progressive error compensation function which integrates the first harmonic fitting and the second harmonic fitting is obtained. An experiment is performed to verify the proposed calibration and compensation methods. The peak-to-peak value of the compensated angle measurement error of the single reading head can be reduced by about 93.76%, which approximates to the error of the mean value of the double reading heads. The experimental results show that the error calibration and compensation method based on the proposed error model can effectively compensate the angle measurement error of the circular grating with a single reading head, and obtain a high-precision measurement angle.

Effects of xenoestrogens on the expression of vitellogenin (vtg) and cytochrome P450 aromatase (cyp19a and b) genes in zebrafish (Danio rerio) larvae.

In the present study, expression levels of vitellogenin (vtg) and cytochrome P450 aromatase genes (cyp19a and cyp19b) in zebrafish larvae during the early stages of development were investigated by quantitative real time-PCR assay. The results indicated that vtg gene transcription was induced seven days after zebrafish larvae fertilization, whereas the expression of cyp19a and cyp19b genes was detected as early as 3 and 4 days post-fertilization (dpf). Investigations into the effects of 17ß-estradiol (E2) exposure on the expression of these genes showed that both vtg and cyp19b were upregulated by E2 in zebrafish larvae as early as four dpf, whereas no variation was observed in cyp19a gene expression. The estrogenic potential of pharmaceutical estrogen (DES), phenol estrogen (BPA) and the brominated flame retardants, TBBPA, DE-71 and 4-BP, were evaluated by analyzing the expression of these three genes in zebrafish larvae. The results demonstrated that natural estrogen, endocrine disrupting compounds and brominated flame retardants act as endocrine disrupters through different mechanisms. We have demonstrated for the first time that the polybrominated diphenyl ether mixture, DE-71, acts as an endocrine disrupter by upregulation of cyp19b gene expression at a relatively low concentration. These results indicate that analysis of vtg and cyp19b gene expression in zebrafish during early embryogenesis and organogenesis represents the basis of a sensitive and fast bioassay for the routine assessment of xenoestrogen effects.