Resonant waveguide grating reflection filter with a quasi-rectangular spectrum under fully conical incidence.

We present the design, analysis, and characterization of a filter with a quasi-rectangular spectrum. The spectral features of the filter are achieved by adjusting the incident angle under fully conical incidence. When the incident angle is 75°, the filter with a quasi-rectangular spectrum is presented at the central wavelength of 475 nm. The proposed filter has a bandwidth of 7.3 nm (R>90%), its corresponding Δλ/λ is approximately 1.5%, and the estimated rejection ratio is larger than 10 dB. Furthermore, the quasi-rectangular filtering feature is stable in the incident angle range of 75° to 85°. Our approach reveals the quasi-rectangular spectrum attributes of double resonance peaks merger under fully conical incidence and thus can be used to exploit filter devices.

Transmission filter controlled by incident conditions in single-layer waveguide grating structures.

The classical single-layer waveguide grating structure is often designed as a reflection filter under 0° azimuthal angle conditions. A new method for achieving a transmission filter by modulating incident conditions is proposed rather than adjusting structural parameters. A 90° azimuthal angle ensures single resonance peaks, and large incident angles provide a low-transmittance background. When the proposed single-layer waveguide grating structure is irradiated with an incident light azimuthal angle of 90° and incident angle of 86°, numerical results show that a high transmission peak emerges at 1550 nm with linewidth $\Delta \lambda = 7.2\,\,{\rm nm}$Δλ=7.2nm. Moreover, the transmission peak has nearly 100% transmittance. These findings show that modulating the incident conditions is also an effective means apart from optimizing the structural parameters. The classical reflection filter can be reversed into a transmission filter using this method.

Simultaneous amplification of DNA in a multiplex circular array shaped continuous flow PCR microfluidic chip for on-site detection of bacterial.

Based on time to place conversion, continuous flow polymerase chain reaction (CF-PCR) can realize a rapid amplification of DNA by running the PCR reagent in a serpentine microchannel but a larger space is required for each sample, which greatly reduces the efficiency of the CF-PCR. Herein, we propose a multiplex circular array shaped CF-PCR microfluidic chip for on-site detection of bacteria. There were 12 serpentine microchannels which were distributed on the disc in an annular form, and each microchannel consisted of an inlet for sample injection, and an outlet for the detection of the PCR products based on fluorescence. Samples could be simultaneously driven into each inlet by a one-to-twelve diverter through a syringe. Moreover, the method of adding fluorescent dyes at the end of the microchannel can solve the inhibition effect of excessive fluorescent dyes on the PCR reaction. The process finished with simultaneous amplification of 12 different target genes from Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Escherichia coli, and on-site detection of their corresponding positives within 23 min. The fastest detectable PCR reaction time was 5.38 ± 0.2 min at a flow rate of 1 mL h-1. For E. coli, the minimum detectable concentration was 2.5 × 10-3 ng µL-1 in this microfluidic system. Such a system can increase the throughput of CF-PCR for point-of-care testing of pathogens.

[Resonance wavelength effects on sensitivity of resonant grating waveguide biosensor].

Resonant grating waveguide (RGW) biosensor has been widely investigated in recent years. The system has several advantages such as minimizing, label-free, high throughput, real time monitoring and so on. The sensitivity of RGW biosensor was theoretically analyzed for different resonance wavelength. Sensitivity to the refractive index and thickness of the sample was analyzed using rigorous coupled wave analysis method. Results indicate that the sensitivity to refractive index is constant for a certain resonance wavelength as the thickness of sample does not change. The sensitivity to refractive index is enhanced with the increase of resonance wavelength. RGW with 1 250 nm resonance wavelength is approximately 4 times as sensitive as RGW with 830 nm resonance wavelength. The sensitivity to thickness drastically decreased at first, and then achieved zero for a certain resonance wavelength as the refractive index of sample is invariable. It was showed that it is limited to test sample thickness for every RGW. RGW with 1 250 nm resonance wavelength is approximately 2 times the measure range as RGW with 830 nm resonance wavelength. The sensitivity to thickness is enhanced with the increase of resonance wavelength. RGW with 1 250 nm resonance wavelength is approximately 3 times as sensitive as RGW with 830 nm resonance wavelength. The above results reveal that the sensitivity to both sample refractive index and sample thickness is enhanced with the increase of resonance wavelength. And the capability of testing sample thickness improves with longer resonance wavelength. The results provided the theory basis for resonance wavelength choice of RGW biosensor.

Study on Chinese Farmland Ecosystem Service Value Transfer Based on Meta Analysis.

An analytic database was built based on meta-regression analysis (MRA) method, mainly including ecosystem service type, farmland division, cultivated land type, value assessment method, and farmland characteristics. The feasible weighted least square (FWLS) method was adopted to comprehensively investigate the seventy observations from empirical studies. The results indicate that: (1) except the negative impact of farmland area on farmland value, such factors as paddy field, good soil conservation function, mainly providing agricultural products, and using market value method for assessment all produce positive effect on the promotion of farmland value. (2) In meta-regression analysis, the average transfer error is 36.74%, and the median transfer error is 14.59%. (3) Under the A1B, A2, B1, and B2 scenarios of IPCC SRES, it is discovered from calculation that the value changes under different scenarios have some differences, in which, the total value rises significantly under A2 scenario and will reach to 15,220 billion yuan until the year of 2100; while the total value loss is the greatest under B1 scenario and will fall to 6320 billion yuan until the year of 2100. Finally, this paper gives some suggestions for scholars to deeply study the service value of farmland ecosystem as well as for the government to formulate differentiation policies.

Dual-wavelength microarray fluorescence detection system using volume holographic filter.

A dual-wavelength microarray scanner based on laser confocal principle is constructed to acquire the laser-induced two-color fluorescence from dyes Cy3 and Cy5. Unlike most commercially available micoarray scanners whose lasers are continuous wave, filters are bandpass and the channels are multiple photomultiplier tubes (PMTs), the system mainly consists of two diode lasers, four volume holographic band-stop filters, and one PMT. The central wavelengths of two kinds of volume holographic band-stop filters are equal to those of the two laser, respectively. The fluorescence beams can pass through the filters, while laser beams are blocked by them because the filters are cut off. The two fluorescences can pass through a common optical path. Thus, only one pinhole and one PMT are required. The two fluorescences are acquired by the PMT with time sharing. The two respective fluorescences can be gathered when two diode lasers work asynchronously. If lasers work synchronously, the two wavelength fluorescences could be acquired simultaneously by the same PMT. A synthesis of a two-color fluorescence image can be realized straightforwardly in this manner. An experiment is conducted and Cy3 and Cy5 fluorescences are captured. Gridding of the fluorescent images based on basic morphological erosion appropriately locates the boundary between adjacent spots.

Optimal classification for the diagnosis of duchenne muscular dystrophy images using support vector machines.

BACKGROUND: This study aimed to investigate the optimal support vector machines (SVM)-based classifier of duchenne muscular dystrophy (DMD) magnetic resonance imaging (MRI) images. METHODS: T1-weighted (T1W) and T2-weighted (T2W) images of the 15 boys with DMD and 15 normal controls were obtained. Textural features of the images were extracted and wavelet decomposed, and then, principal features were selected. Scale transform was then performed for MRI images. Afterward, SVM-based classifiers of MRI images were analyzed based on the radical basis function and decomposition levels. The cost (C) parameter and kernel parameter [Formula: see text] were used for classification. Then, the optimal SVM-based classifier, expressed as [Formula: see text]), was identified by performance evaluation (sensitivity, specificity and accuracy). RESULTS: Eight of 12 textural features were selected as principal features (eigenvalues [Formula: see text]). The 16 SVM-based classifiers were obtained using combination of (C, [Formula: see text]), and those with lower C and [Formula: see text] values showed higher performances, especially classifier of [Formula: see text]). The SVM-based classifiers of T1W images showed higher performance than T1W images at the same decomposition level. The T1W images in classifier of [Formula: see text]) at level 2 decomposition showed the highest performance of all, and its overall correct sensitivity, specificity, and accuracy reached 96.9, 97.3, and 97.1 %, respectively. CONCLUSION: The T1W images in SVM-based classifier [Formula: see text] at level 2 decomposition showed the highest performance of all, demonstrating that it was the optimal classification for the diagnosis of DMD.

Correction of image distortions in endoscopic optical coherence tomography based on two-axis scanning MEMS mirrors.

A two-axis scanning microelectromechanical (MEMS) mirror enables an optical coherence tomography (OCT) system to perform three-dimensional endoscopic imaging due to its fast scan speed and small size. However, the radial scan from the MEMS mirror causes various distortions in OCT images, namely spherical, fan-shaped and keystone distortions. In this paper, a new method is proposed to correct all of three distortions presented in OCT systems based on two-axis MEMS scanning mirrors. The spherical distortion is corrected first by directly manipulating the original spectral interferograms in the phase domain, followed by Fourier transform and three-dimensional geometrical transformation for correcting the other two types of distortions. OCT imaging experiments on a paper with square ink printed arrays and a glass tube filled with milk have been used to validate the proposed method. Distortions in OCT images of flat or curved surfaces can all be effectively removed.

Optimization of chelator-assisted phytoextraction, using EDTA, lead and Sedum alfredii Hance as a model system.

Pot and leaching column experiments were conducted to optimize chelator-assisted phytoextraction of lead (Pb) from contaminated soils. Optimum phytoextraction occurred at added EDTA concentration of 5 mM in single dose for 10 days in low Pb soil (treated with 400 mg kg(-1) soil), while it would be better for high Pb soil (treated with 1,200 mg kg(-1) soil) with five intermittent doses of 10 mM EDTA for 7 days. Combined with column experiment, it could be inferred that chelator-assisted phytoextraction is more suitable for the slightly contaminated soils.