Optical information hiding for different surface images.

Optical hiding often requires the selection of specific artificial optical components as carriers, which results in poor versatility of the carriers and high costs for the hiding system. To conceal secret information on different surfaces such as metal, wood, and paper, we propose an optical information hiding method. In this method, we use images of surfaces, whose grayscale histograms have the characteristic of symmetric distribution. Based on this characteristic, we first scramble the surface image, and then adjust part of the gray value of the surface image to the complementary value to embed the secret information into a scrambled surface image to generate a key image. In the extraction process, a projector is used to reproduce the scrambled surface image and the key image, which are then incoherently superimposed to extract the secret information using the human visual system. The extraction process does not require complex optical knowledge and is simple and feasible. Simulation experiments and optical experiments indicate that this method is applicable in practice and possesses good security and imperceptibility. Furthermore, we prove the reliability of this method by embedding secret information in different surface images, demonstrating the potential application of more surface images in the field of optical information hiding. Finally, we discuss the applicability of surface information images and analyze the imperceptibility of key images.

Binocular full-color holographic three-dimensional near eye display using a single SLM.

A binocular full-color holographic three-dimensional near eye display system using a single spatial light modulator (SLM) is proposed. In the display system, the frequency spectrum shifting operation and color spectrum shifting operation are adopted to realize the frequency division multiplexing (FDM) and frequency superposition multiplexing (FSM) by manipulating the frequency spectrums of each color- and view-channel sub-holograms. The FDM combined with polarization multiplexing will be used to implement binocular display using a single SLM, and the FSM working with a bandpass filter for each view-channel will be used to achieve full-color display from single frame hologram. The optical analysis and experiments with 3D color objects confirm the feasibility of the proposed system in the practical application.

[A new xanthone from hulls of Garcinia mangostana and its cytotoxic activity].

Eight compounds were isolated from ethyl acetate fraction of 80% ethanol extract of the hulls of Garcinia mangostana by silica gel, Sephadex LH-20 column chromatography, as well as prep-HPLC methods. By HR-ESI-MS, MS, 1D and 2D NMR spectral analyses, the structures of the eight compounds were identified as 16-en mangostenone E(1), α-mangostin(2), 1,7-dihydroxy-2-(3-methy-lbut-2-enyl)-3-methoxyxanthone(3), cratoxyxanthone(4), 2,6-dimethoxy-para-benzoquinone(5), methyl orselinate(6), ficusol(7), and 4-(4-carboxy-2-methoxyphenoxy)-3,5-dimethoxybenzoic acid(8). Compound 1 was a new xanthone, and compound 4 was a xanthone dimer, compound 5 was a naphthoquinone. All compounds were isolated from this plant for the first time except compounds 2 and 3. Cytotoxic bioassay suggested that compounds 1, 2 and 4 possessed moderate cytotoxicity, suppressing HeLa cell line with IC_(50) va-lues of 24.3, 35.5 and 17.1 µmol·L~(-1), respectively. Compound 4 also could suppress K562 cells with an IC_(50) value of 39.8 µmol·L~(-1).

ANGPTL4 regulate glutamine metabolism and fatty acid oxidation in nonsmall cell lung cancer cells.

Angiopoietin-like protein (ANGPTL) 4 is a key factor in the regulation of lipid and glucose metabolism in metabolic diseases. ANGPTL4 is highly expressed in various cancers, but the regulation of energy metabolism in tumours remains to be determined. This study explored the role of ANGPTL4 in aerobic glycolysis, glutamine consumption and fatty acid oxidation in nonsmall cell lung cancer (NSCLC) cells. Two NSCLC cell lines (A549 and H1299) were used to investigate the role of ANGPTL4 in energy metabolism by tracer techniques and with Seahorse XF technology in ANGPTLs4 knockdown cells. RNA microarrays and specific inhibitors were used to identify targets in ANGPTLs4-overexpressing cells. The results showed that knockdown of ANGPTLs4 could inhibit energy metabolism and proliferation in NSCLC. ANGPTLs4 had no significant effect on glycolysis but affected glutamine consumption and fatty acid oxidation. Knockdown of ANGPTLs4 also significantly inhibited tumour metastasis and energy metabolism in mice and had a weak effect on glycolysis. RNA microarray analysis showed that ANGPTLs4 significantly affected glutaminase (GLS) and carnitine palmitoyl transferase 1 (CPT1). ANGPTLs4-overexpressing cells were exposed to a glutamine deprivation environment, and cell proliferation and energy metabolism were significantly decreased but still differed from normal NSCLC cells. Treatment of ANGPTLs4-overexpressing cells with GLS and CPT1 inhibitors simultaneously prevented the regulatory effects on cell proliferation and energy metabolism. ANGPTLs4 could promote glutamine consumption and fatty acid oxidation but not glycolysis or accelerate energy metabolism in NSCLC.

3D image reconstruction of terahertz computed tomography at sparse angles by total variation minimization.

Continuous-wave terahertz computed tomography (THz-CT) is an important three-dimensional imaging method for probing the profile and inner properties of a sample's structure. We applied the total variation (TV) minimization iterative algorithm to squeeze 75% data acquisition time of THz-CT without the loss of reconstruction fidelity. The imaging system is built based on a 278.6 GHz avalanche diode source. A zero-order Bessel beam is generated by an axicon, for which the intensity profile remains essentially propagation invariant within the non-diffracting zone. The effectiveness of the proposed method is verified by using three optically opaque objects. The reconstruction results show that the TV-minimization algorithm can effectively suppress noise, artefacts, and shape distortion created in sparse angle reconstruction.

Full-field high-resolution terahertz imaging based on a high-resistance silicon solid immersion lens.

The spatial resolution of the direct imaging system depends on the wavelength and the numerical aperture. In the terahertz (THz) waveband, the wavelength is relatively large, and the higher numerical aperture of the imaging system usually promises the possibility of achieving higher spatial resolution. Solid immersion technique is an effective method to expand the numerical aperture. We design and fabricate a hemisphere lens with high-resistance silicon to achieve the effect of solid immersion, and obtain full-field, high-resolution focal-plane imaging. The characteristics of the direct refraction imaging and the secondary reflection imaging are analyzed by ray-tracing calculations. And the field curvature of the equivalent object plane and the spot diagram on the vertical image plane of the lens are quantifiably evaluated. It is shown that the secondary reflection imaging can effectively reduce the geometric distortion and achieve more ideal imaging quality. The method of blocking different regions before and after the solid immersion lens is proposed to obtain a clear magnified image of a two-dimensional grating with the period of 300 µm. This method provides a powerful tool for THz full-field microscopic imaging.

Simultaneous detection of the distance and direction for a noncooperative target based on the microwave photonic radar.

For a noncooperative target, multiple-dimension detection is required to determine its spatial location. A microwave photonic radar is proposed for simultaneous detection of the distance and direction of targets. At the transmitter, a linear frequency modulation (LFM) signal with a large instantaneous bandwidth was obtained by frequency doubling. Meanwhile, the optical reference signal was supplied. At the receiver, two antennas with a certain baseline length were used to receive the echo signal. The dechirp process and fixed-length cable are combined to decouple the distance and direction and distinguish between the positive and negative directions of a target. Theoretical derivation has already verified that the distance and direction can be resolved simultaneously by dechirping of the echo modulation signal and reference signal. In experiments, an LFM signal with an instantaneous bandwidth of 2 GHz (2-4 GHz) was generated and launched as the detection signal. Targets at different distances with positive and negative angles were detected. The results show that the directional measurement ranges from -72.5° to 72.5°, and the error is less than 1.6°. The measured distance was found to be quite similar to the actual distance. The proposed approach can confirm the spatial location of a noncooperative target by combining the detection of both distance and direction. Furthermore, the baseline length need not be less than half the wavelength of the echo signal, and large antennas can be chosen to improve the detection distance and range accuracy.

Transport of intensity equation-based terahertz lensless full-field phase imaging.

Terahertz (THz) phase imaging is widely spreading in various scenarios, among which full-field phase distributions are commonly retrieved by digital holography or ptychography. In this Letter, the transport of the intensity equation reconstruction method is applied into the THz band. An algorithm named the lensless US-transport of intensity equation (TIE) is proposed to accommodate to an in-line configuration. The object phase is retrieved by primarily conducting iterations between the axial intensity derivative and the phase distribution at the recording plane and subsequent backward diffraction propagation. This method is applicable to both isolated and extended weakly absorbing samples with higher reconstruction quality and remarkably less time cost than holographic phase retrieval algorithms. It can also be attempted in other non-interferometric geometries or using low-cost partially coherent THz sources, which significantly broaden the application scope of THz phase imaging.

Chemoselective synthesis of 5,4'-imidazolinyl spirobarbiturates via NBS-promoted cyclization of unsaturated barbiturates and amidines.

A selective cyclization of unsaturated barbiturates and amidines promoted by N-bromosuccinimide has been successfully developed to afford a vast variety of 5,4'-imidazolinyl spirobarbiturates in moderate to good yields. The present protocol features broad substrate scope, facile work-up procedure and mild reaction conditions, providing a novel strategy for the highly selective and efficient construction of structurally diverse spiroimidazolines.

Continuous-wave terahertz self-referencing digital holography based on Fresnel's mirrors.

Continuous-wave terahertz digital holography (TDH) is a booming full-field phase-contrast imaging method validated in both in-line and Mach-Zehnder off-axis geometries. In this Letter, a self-referencing TDH approach is proposed based on the Fresnel's mirrors, by which the object wavefront is partitioned and reflected. Two beams interfere with each other to form an off-axis hologram. The proposed recording configuration is immune from a superposed twin image and has higher temporal stability than Mach-Zehnder interferometers. To evaluate the phase-contrast imaging performance, different types of samples are measured.

Continuous-wave terahertz reflective ptychography by oblique illumination.

Massive usage scenarios prompt the prosperity of terahertz (THz) reflective imaging methods. In this Letter, we apply ptychography to continuous-wave THz reflective imaging. Our scheme has a compact lensless layout and uses a full-field oblique-illumination recording mode. Diffraction patterns are corrected through tilted plane correction. This method can be used to retrieve the complex-valued object function and to suppress the negative effect of non-uniform illumination. The feasibility is investigated using two metal samples.

Multi-layered full-field phase imaging using continuous-wave terahertz ptychography.

Due to the unique properties of terahertz (THz) waves, THz phase imaging has been widely investigated to retrieve the absorption and phase modulation of dielectric two-dimensional thin samples, as well as multiple stacked samples. In this Letter, we apply the three-dimensional ptychographic iterative engine algorithm for continuous-wave THz full-field multi-layered phase imaging. The complex-valued transmission function of two-layered polypropylene thin plates and the corresponding probe function are reconstructed, respectively, which are immune to crosstalk of different layers. The phenomenon of the field-of-view enlargement at the second object layer is observed. This lensless compact imaging method can be potentially used for THz three-dimensional imaging.

[Study on GLI values of Polygonatum odoratum base on multi-temporal of unmanned aerial vehicle remote sensing].

Unmanned aerial vehicle(UAV) remote sensing and vegetation index have great potential in the field of Chinese herbal medicine planting. In this study, the visible light image of Polygonatum odoratum planting area in Changyi district of Jilin province were acquired by UAV, and the real-time monitoring of P. odoratum planting area was realized. The green leaf index(GLI) was established, and GLI values of P. odoratum were collected used the spatial sampling points. To compare the GLI values in different periods, it was found that the GLI values of P. odoratum have three stages changing rule of rising-gentle-falling related to the germination, vigorous growth and withered of P. odoratum growth. Meanwhile, the GLI values were compared with four biomass data of P. odoratum, including plant height, leaf area, chlorophyll a and chlorophyll b content in leaves, and it was found that the GLI value was related to the growth potential of P. odoratum. The GLI value with a rapid increase in rising stage or at a high level in the gentle stage means the P. odoratum was in a better growth potential. GLI value has a same change trend with plant height, and has certain correlation with plant height and leaf area. However, there is no obvious relationship between chlorophyll a and chlorophyll b contents in leaves and GLI value. The study clarified the change rule of GLI value of P. odoratum, explained the reason for the change of GLI value, and expanded the application range of GLI. The research shows that UAV and vegetation index can be applied to monitoring the Chinese herbal medicines planting, and provides a new idea for exploring more effective information extraction methods of Chinese herbal medicines.

Probe position correction based on overlapped object wavefront cross-correlation for continuous-wave terahertz ptychography.

Continuous-wave terahertz ptychography is a promising large field-of-view lensless terahertz phase imaging method. Inaccurate probe positions would severely degrade the reconstruction quality, as compared to other spectral bands. In this paper, we propose a probe position correction method based on cross-correlation registration on overlapped regions of the object wavefront for terahertz ptychography. The translation errors could be minimized in the order of 0.01 pixels. The simulation results suggest good computational efficiency, correction, and reconstruction accuracy. We perform continuous-wave terahertz ptychography on a cicada's forewing. The subcosta and the first radius vein are distinguished after position correction. The probe position distribution reveals that the tilt angle between the object plane and the recording plane is 0.26°.

THz coherent lensless imaging.

Imaging with THz radiation has proved an important tool for both fundamental science and industrial use. Here we review a class of THz imaging implementations, named coherent lensless imaging, that reconstruct the coherent response of arbitrary samples with a minimized experimental setup based only on a coherent source and a camera. After discussing the appropriate sources and detectors to perform them, we detail the fundamental principles and implementations of THz digital holography and phase retrieval. These techniques owe a lot to imaging with different wavelengths, yet innovative concepts are also being developed in the THz range and are ready to be applied in other spectral ranges. This makes our review useful for both the THz and imaging communities, and we hope it will foster their interaction.

Stochastic dual-plane on-axis digital holographic imaging on irregular surfaces.

An imaging method based on dual-plane on-axis digital holography is proposed for the situation in which an object is on the irregular surface of a transparent medium. Light propagation of the object on the uneven surface of the medium is analyzed and simulated. The diffracted pattern of the object is deformed or destroyed by the refracted light of the medium. Dual-plane on-axis digital holography is used to eliminate the twin image. In order to retrieve the information lost in the reconstructed image due to destructive interference, the object is illuminated by a stochastic beam that is a speckle wave produced by a ground glass. Simulated and experimental results are presented, to demonstrate that the proposed method can be used for imaging on the irregular surface of a transparent medium.

Synthetic aperture in terahertz in-line digital holography for resolution enhancement.

Terahertz digital holography is a combination of terahertz technology and digital holography. In digital holography, the imaging resolution is the key parameter in determining the detailed quality of a reconstructed wavefront. In this paper, the synthetic aperture method is used in terahertz digital holography and the in-line arrangement is built to perform the detection. The resolved capability of previous terahertz digital holographic systems restricts this technique to meet the requirement of practical detection. In contrast, the experimental resolved power of the present method can reach 125 µm, which is the best resolution of terahertz digital holography to date. Furthermore, the basic detection of a biological specimen is conducted to show the practical application. In all, the results of the proposed method demonstrate the enhancement of experimental imaging resolution and that the amplitude and phase distributions of the fine structure of samples can be reconstructed by using terahertz digital holography.

Terahertz in-line digital holography of dragonfly hindwing: amplitude and phase reconstruction at enhanced resolution by extrapolation.

We report here on terahertz (THz) digital holography on a biological specimen. A continuous-wave (CW) THz in-line holographic setup was built based on a 2.52 THz CO(2) pumped THz laser and a pyroelectric array detector. We introduced novel statistical method of obtaining true intensity values for the pyroelectric array detector's pixels. Absorption and phase-shifting images of a dragonfly's hindwing were reconstructed simultaneously from single in-line hologram. Furthermore, we applied phase retrieval routines to eliminate twin image and enhanced the resolution of the reconstructions by hologram extrapolation beyond the detector area. The finest observed features are 35 µm width cross veins.

Dual-plane in-line digital holography based on liquid crystal on silicon spatial light modulator.

A dual-plane in-line digital holographic method is proposed with a liquid crystal on silicon (LCOS) spatial light modulator (SLM) for recording holograms at two slightly displaced planes. The computer-generated chirp-like complex reflectance is displayed on the LCOS SLM to adapt the object beam at two planes for recording two holograms processed to eliminate the DC term and twin image accurately; no mechanical components or manual operation during data acquisition is required. The proposed approach improves the speed, accuracy, and stability of the experiment. Computer simulation and experiments for both amplitude and phase objects are carried out to validate the proposed method.

Intravesical hyaluronidase causes chronic cystitis in a rat model: a potential model of bladder pain syndrome/interstitial cystitis.

OBJECTIVES: To determine whether a potential rat model of bladder pain syndrome could be developed through long-term intermittent intravesical hyaluronidase. METHODS: A total of 64 female Sprague-Dawley rats were divided into a control group, a low-dose hyaluronidase (1 mg/mL) group, a high-dose hyaluronidase (4 mg/mL) group and a hyaluronic acid-treated group. Hyaluronidase was given intravesically three times a week for 1 month. Hyaluronic acid (0.5 mL, 0.8 mg/mL) was introduced intravesically to hyaluronidase-treated rats' bladders. Histological changes, cystometry, nociceptive behaviors, and messenger ribonucleic acid levels of inflammatory factors were evaluated and compared between groups. RESULTS: All hyaluronidase-treated rats showed chronic inflammation and fibrosis, increased and activated mast cells, thinned bladder epithelium with abnormal expressions of uroplakin III and zonula occluden-1, and increased levels of interleukin-6 and intercellular adhesion molecule-1 messenger ribonucleic acid. However, the inflammatory score and levels of interleukin-6 and intercellular adhesion molecule-1 were more significant in the high-dose hyaluronidase group than in the low-dose hyaluronidase group (P < 0.01). Furthermore, hyaluronidase-treated rats showed markedly decreased intercontraction intervals, bladder capacity and increased sensitivity to pain compared with controls (P < 0.01). Hyaluronic acid treatment significantly decreased the inflammatory level, number of mast cells, sensitivity to pain, levels of interleukin-6 and intercellular adhesion molecule-1, and increased intercontraction intervals and bladder capacity (P < 0.01). CONCLUSIONS: Long-term intermittent intravesical hyaluronidase could develop a severe chronic cystitis with diffused fibrosis accompanied by altered histology and bladder function. This chronic cystitis rat model can resemble the clinical and histopathological features of human bladder pain syndrome, and might be a potential valuable model for investigation of this troublesome disease.