Compact freeform-surface-based Offner imaging spectrometer with both a long-slit and broadband.

Current imaging spectrometers with conventional optical elements face major challenges in achieving a large field of view (FOV), broadband and compact structure simultaneously. In this paper, a compact freeform-surface-based Offner imaging spectrometer with both a long-slit and a broadband (CISLS) is proposed. To keep a long slit and an anastigmatic imaging, the slit off-axis amount of the initial system is within a specific range theoretically. While to achieve a compact structure, the slit off-axis amount should be away from the specific range and as small as possible. Based on the vector aberration theory and the analytical study, Zernike polynomial terms Z5 and Z6 introduce the astigmatism independent of FOV. They are utilized to well balance the astigmatism when the slit off-axis amount is away from the specific range, helping a miniaturization of the system. Other Zernike polynomial terms below the eighth order introduce the astigmatism related to FOV. They contribute to balancing the astigmatism that produced with the increasing of the FOV, thus achieving a wide FOV. The design results show that the proposed CISLS with a high spectral resolution of 2.7 nm achieves a long slit of 30 mm in length but a small size of only 60 mm × 64 mm × 90 mm in volume under a broadband from 400 nm to 1000 nm.

Compact multi-spectral-resolution Wynne-Offner imaging spectrometer with a long slit.

Current imaging spectrometers are developed towards a large field of view (FOV) as well as high resolution to obtain more spatial and spectral information. However, imaging spectrometers with a large FOV and high resolution produce a huge image data cube, which increases the difficulty of spectral data acquisition and processing. In practical applications, it is more reasonable and helpful to identify different targets within a large FOV with different spectral resolutions. In this paper, a compact multi-spectral-resolution Wynne-Offner imaging spectrometer with a long slit is proposed by introducing a special diffraction grating with multi-groove densities at different areas. With the increasing of the groove density and the slit length, the astigmatism of the Wynne-Offner imaging spectrometer increases sharply. Therefore, the relationships between the astigmatism and both the groove density and slit length are studied. Moreover, a holographic grating is introduced. The holographic aberrations produced are utilized to balance the residual astigmatism of the imaging spectrometer. The design results show that the system is only 60m m×115m m×103m m in volume but achieves both a long slit of 20 mm in length and a waveband from 400 nm to 760 nm with three kinds of spectral resolutions of 2 nm, 1 nm, and 0.5 nm. The designed compact multi-spectral-resolution Wynne-Offner imaging spectrometer can be widely applied in the fields of crop classification and pest detection, which require both a large FOV and multiple spectral resolutions.

Ultra-compact dual band imaging spectrometer with freeform prisms.

Wide spectrum and miniaturization are the main challenges in the imaging spectrometer design. In this paper, we propose an ultra-compact dual band imaging spectrometer (CDBIS) with cemented freeform prisms, which works at both the visible-near-infrared (VNIR) from 400 nm to 1000 nm and the shortwave-infrared (SWIR) from 1000 nm to 1700 nm. The imaging spectrometer is only composed of three cemented prisms, a primary prism and two triangular prisms. And a freeform surface characterized by the Zernike polynomial is introduced in each prism. The CDBIS is dispersed by a diffraction grating, which is designed on the second surface of the primary prism. Based on vector aberration theory (VAT), the relationship among the astigmatism generated by the introduced freeform surfaces, the wavelength, and the field of view is studied. Accordingly, a wideband is realized by introducing the freeform surfaces after the diffraction grating. Furthermore, through optimizing the coefficients of Zernike polynomial terms, residual astigmatism at different wavelengths is well balanced. An imaging spectrometer with a volume of only 100c m 3 is obtained, with a spectral resolution of 1.45 nm at VNIR and 2.40 nm at SWIR, respectively. It has a huge potential for broadband space exploration.

Spatial-spectral resolution tunable snapshot imaging spectrometer: analytical design and implementation.

A snapshot imaging spectrometer is a powerful tool for dynamic target tracking and real-time recognition compared with a scanning imaging spectrometer. However, all the current snapshot spectral imaging techniques suffer from a major trade-off between the spatial and spectral resolutions. In this paper, an integral field snapshot imaging spectrometer (TIF-SIS) with a continuously tunable spatial-spectral resolution and light throughput is proposed and demonstrated. The proposed TIF-SIS is formed by a fore optics, a lenslet array, and a collimated dispersive subsystem. Theoretical analyses indicate that the spatial-spectral resolution and light throughput of the system can be continuously tuned through adjusting the F number of the fore optics, the rotation angle of the lenslet array, or the focal length of the collimating lens. Analytical relationships between the spatial and spectral resolutions and the first-order parameters of the system with different geometric arrangements of the lenslet unit are obtained. An experimental TIF-SIS consisting of a self-fabricated lenslet array with a pixelated scale of 100×100 and a fill factor of 0.716 is built. The experimental results show that the spectral resolution of the system can be steadily improved from 4.17 to 0.82 nm with a data cube (N x×N y×N λ) continuously tuned from 35×35×36 to 40×40×183 in the visible wavelength range from 500 to 650 nm, which is consistent with the theoretical prediction. The proposed method for real-time tuning of the spatial-spectral resolution and light throughput opens new possibilities for broader applications, especially for recognition of things with weak spectral signature and biomedical investigations where a high light throughput and tunable resolution are needed.

Dual-channel snapshot imaging spectrometer with wide spectrum and high resolution.

The comprehensive analysis of dynamic targets brings about the demand for capturing spatial and spectral dimensions of visual information instantaneously, which leads to the emergence of snapshot spectral imaging technologies. While current snapshot systems face major challenges in the development of wide working band range as well as high resolution, our novel dual-channel snapshot imaging spectrometer (DSIS), to the best of our knowlledge, demonstrates the capability to achieve both wide spectrum and high resolution in a compact structure. By dint of the interaction between the working band range and field of view (FOV), reasonable limits on FOV are set to avoid spectral overlap. Further, we develop a dual-channel imaging method specifically for DSIS to separate the whole spectral range into two parts, alleviating the spectral overlap on each image surface, improving the tolerance of the system for a wider working band range, and breaking through structural constraints. In addition, an optimal FOV perpendicular to the dispersion direction is determined by the trade-off between FOV and astigmatism. DSIS enables the acquisition of 53×11 spatial elements with up to 250 spectral channels in a wide spectrum from 400 to 795 nm. The theoretical study and optimal design of DSIS are further evaluated through the simulation experiments of spectral imaging.

Analytical design of a cemented-curved-prism based integral field spectrometer (CIFS) with high numerical aperture and high resolution.

Snapshot hyperspectral imaging is superior to scanning spectrometers due to its advantage in dimensionality, allowing longer pixel dwell time and higher data cube acquisition efficiency. Due to the trade-off between spatial and spectral resolution in snapshot spectral imaging technologies, further improvements in the performance of snapshot imaging spectrometers are limited. Therefore, we propose a cemented-curved-prism-based integral field spectrometer (CIFS), which achieves high spatial and high spectral resolution imaging with a high numerical aperture. It consists of a hemispherical lens, a cemented-curved-prism and a concave spherical mirror. The design idea of aplanatic imaging and sharing-optical-path lays the foundation for CIFS to exhibit high-resolution imaging in a compact structure. The numerical model between the parameters of optical elements and the spectral resolution of the system is established, and we analyze the system resolution influenced by the hemispherical lens and the cemented-curved-prism. Thus, the refractive index requirements of the hemispherical lens and the cemented-curved-prism for the optimal spatial and spectral resolution imaging of the system are obtained, providing guidance for the construction of CIFS. The designed CIFS achieves pupil matching with a 1.8 f-number lenslet array, sampling 268 × 76 spatial points with 403 spectral channels in the wavelength band of 400 to 760 nm. The spectral and spatial resolution are further evaluated through a simulation experiment of spectral imaging based on Zemax. It paves the way for developing integral field spectrometers exhibiting high spatial and high spectral resolution imaging with high numerical aperture.

Non-uniformity correction of wide field of view imaging system.

Requirements for wide field of view (FOV) imaging system reflect the need for both uniform illumination as well as excellent image quality across the entire FOV. As the monocentric lens combined with a parallel array of relay imagers achieves a wide-FOV while maintaining a high resolution, we studied the monocentric cascade imaging system (MCIS). However, the imaging experiment of the prototype shows two issues, including vignetting and non-uniform image quality over the full FOV. They affect the image stitching which is necessary for wide-FOV image acquisition. This paper studies how the position of the aperture stop affects the vignetting and the local aberrations in MCIS. Moving laws of the aperture stop and its relationship with the local aberrations are presented. Moreover, aspheric surfaces on proper surfaces are introduced and studied to balance the local aberrations. Accordingly, an MCIS with uniform illumination and good image quality is presented. The MCIS achieves a wide-FOV of 116.4° and an instantaneous FOV of 0.0021°. It keeps a relative illumination exceeding 97% during the full FOV. The modulation transfer function (MTF) is over 0.285 at the Nyquist frequency of 270 lp/mm. This paper provides a profound theorical reference for further applications and developments of MCIS.

High spectral resolution compact Offner spectrometer based on the aberration-reduced convex holographic gratings recorded by spherical waves under Rowland circle mounting.

High spectral resolution, excellent imaging quality, and compact configuration have become a recent trend in push-broom imaging spectrometers. The concentric Offner imaging spectrometer has become popular due to its high optical performance and compactness. However, astigmatism is the dominant residual aberration in the Offner imaging spectrometer, which makes the meridional and sagittal images unable to be focused well and causes a deterioration in image quality and spectral resolution. In this paper, we present a compact Offner imaging spectrometer with a high resolution based on an aberration-reduced convex holographic grating (ACHG), which is recorded by spherical waves under Rowland circle mounting. The holographic aberration coefficients of ACHG and geometric aberration coefficients of the Offner imaging spectrometer are derived based on the analysis of the light-path function. Furthermore, we analyzed the relationship between holographic aberration coefficients and holographic recording parameters of ACHG under Rowland circle mounting. To balance the geometric aberration of the Offner imaging spectrometer, proper holographic aberration coefficients of the ACHG are achieved through adjusting the holographic recording parameters. The design result indicated that the Offner imaging spectrometer with ACHG provides better images than those with mechanically ruled convex grating (MRCG). Moreover, the spectral resolution is significantly improved. This lays down a theoretical basis for subsequent construction work in the Offner imaging spectrometer with holographic aberration-reduced gratings.

Extracellular ubiquitin protects cardiomyocytes during ischemia/hypoxia by inhibiting mitochondrial apoptosis pathway through CXCR4.

AIM: Acute myocardial infarction (AMI) is one of the deadliest diseases worldwide. The search for countermeasures to reduce cardiomyocytes death in the infarcted area has always been the focus of research. Ubiquitin (UB) is a small polypeptide mainly involved in proteasome-mediated protein degradation in cells, whereas extracellular UB in body fluids can also function through its receptor CXC chemokine receptor type 4 (CXCR4). This study aimed to explore the functional roles of extracellular UB in cardiomyocytes during ischemia/hypoxia (I/H). METHODS: H9C2 cells were subjected to I/H treatment and cell injury was evaluated by cell viability, morphology changes and apoptosis rate. UB expression and levels of ubiquitinated proteins after I/H injury were measured. The effects of extracellular UB on I/H-induced cardiomyocytes apoptosis and the possible underlying mechanisms were studied. RESULTS: I/H injury induced the decrease of cell viability as well as enhanced impaired cell morphology and apoptosis rate in H9C2 cells. Levels of UB mRNA and ubiquitinated proteins were significantly up-regulated after I/H treatment, whereas the concentration of extracellular UB in the conditioned media did not show significant change and the intracellular mono-UB levels in cells were down-regulated. Extracellular UB treatment protected cardiomyocytes from I/H injury by inhibiting the overactivation of mitochondria-dependent apoptosis pathway and up-regulating autophagy level. Inhibition of CXCR4 receptor using AMD3100 abolished cardioprotective effects of extracellular UB. CONCLUSION: The up-regulation of UB was suggested to be an adaptive response to resist I/H-induced cardiomyocytes apoptosis, and additional extracellular UB treatment might serve as a new potential therapeutic drug for AMI.

Iterative local Fourier transform-based high-accuracy wavelength calibration for Fourier transform imaging spectrometer.

An iterative local Fourier transform (ILFT)-based high-accuracy wavelength calibration for Fourier transform imaging spectrometer (FTIS) is proposed. The wavelength calibration for FTIS is to determine the relation between the wavelength and the wavenumber position. However, the wavenumber position solved by conventional method is only accurate up to integers restricted by the picket-fence effect of discrete Fourier transform. While the proposed ILFT can increase the accuracy of calculating the wavenumber position by combining the local Fourier transform and a few iterations. In this paper, the method is investigated in theory and then by simulations and experiments. The simulations show that the accuracy of the wavenumber position calculated by the ILFT is increased by 100 times than conventional method with noise, phase error, and non-uniform sampling of optical path difference. And the experimental results indicate that the ILFT decreases the absolute error of wavelength calibration from about 2.03 nm to 0.16 nm. Therefore, the method provides theoretical and technical support for FTIS and promotes the development of superior resolutions therein.

Extracellular ubiquitin levels are increased in coronary heart disease and associated with the severity of the disease.

Aim: This study aimed to evaluate concentration of plasma extracellular ubiquitin (UB) in coronary heart disease (CHD) patients and its correlation with the disease severity.Methods: Levels of UB and stromal cell-derived factor-1a (SDF-1a) were measured in 60 healthy controls and 67 CHD cases. Coronary atherosclerosis was assessed with Gensini scoring system. Spearman correlation was used to evaluate the correlation between UB and low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), creatine kinase-MB (CK-MB), cardiac troponin I (cTnI) or SDF-1a. The receiver-operating characteristic (ROC) curve was established to assess the predictive value of UB.Results: Plasma UB levels were significantly higher in CHD patients than in controls (p < .0001), and the levels in those with acute myocardial infarction (AMI) were higher than stable angina pectoris (SAP) and unstable angina pectoris (UAP) groups (both p < .01). UB was also positively correlated with Gensini score, CRP, CK-MB and cTnI in CHD. ROC analysis of UB showed that the area under the curve (AUC) were 0.711 (95%CI, 0.623-0.799) and 0.778 (95%CI, 0.666-0.890) for CHD and acute coronary syndrome (ACS), respectively. Plasma SDF-1a levels were elevated in CHD patients but showed no significant correlation with UB concentration or the severity of the disease.Conclusion: Plasma UB concentration was increased in CHD and the change of UB levels may reflect the progression of CHD.

Efficient Optical Reflection Modulation by Coupling Interband Transition of Graphene to Magnetic Resonance in Metamaterials.

Designing powerful electromagnetic wave modulators is required for the advancement of optical communication technology. In this work, we study how to efficiently modulate the amplitude of electromagnetic waves in near-infrared region, by the interactions between the interband transition of graphene and the magnetic dipole resonance in metamaterials. The reflection spectra of metamaterials could be significantly reduced in the wavelength range below the interband transition, because the enhanced electromagnetic fields from the magnetic dipole resonance greatly increase the light absorption in graphene. The maximum modulation depth of reflection spectra can reach to about 40% near the resonance wavelength of magnetic dipole, for the interband transition to approach the magnetic dipole resonance, when an external voltage is applied to change the Fermi energy of graphene.

[Assessment of groundwater quality of different aquifers in Tongzhou area in Beijing Plain and its chemical characteristics analysis].

In order to evaluate the groundwater quality of Tongzhou area in Beijing Plain and to discuss the characteristics of its distribution by the view of hydrochemistry, a total of 151 groundwater samples, collected within study area in the dry period of 2008 according to the geological and hydrogeololgical condition of Tongzhou area, were classified as shallow, middle and deep groundwater, respectively. Based on the data, the groundwater quality was evaluated by the method of F value. The mean and variance of main chemical constituents of groundwater samples were presented. Almost all the quaternary groundwater of Chaobai river pluvial fan belonged to the alkaline water type. The evaluation results based on the analysis results showed that from shallow to deep, the quality of groundwater in Beijing became better. The total areas of groundwater belonging to class IV and V area were 884 km2, 599 km2 and 94 km2 respectively for shallow, middle and deep groundwater. The evaluation results showed that the main exceeding chemical constituents were TDS, hardness, NH4(+), F(-) and total Fe. Most exceeding samples belonged to middle and deep aquifers. The main types of shallow groundwater were HCO2-Ca x Mg- and HCO3 x Cl-Ca x Na x Mg, while the chemical types of mid-deep groundwater were mostly HCO3-Na x Ca- and HCO3 x SO4(2-) -Na x Ca type due to the increased Na(+), SO4(2-) and Cl(-) concentration. Study results showed that the quality of shallow groundwater became worse mainly due to human activities. The deterioration of groundwater quality in mid-deep aquifers was due to both human activities and natural occurrence of poor-quality water.

[Groundwater organic pollution source identification technology system research and application].

Groundwater organic pollutions are found in large amount of locations, and the pollutions are widely spread once onset; which is hard to identify and control. The key process to control and govern groundwater pollution is how to control the sources of pollution and reduce the danger to groundwater. This paper introduced typical contaminated sites as an example; then carried out the source identification studies and established groundwater organic pollution source identification system, finally applied the system to the identification of typical contaminated sites. First, grasp the basis of the contaminated sites of geological and hydrogeological conditions; determine the contaminated sites characteristics of pollutants as carbon tetrachloride, from the large numbers of groundwater analysis and test data; then find the solute transport model of contaminated sites and compound-specific isotope techniques. At last, through groundwater solute transport model and compound-specific isotope technology, determine the distribution of the typical site of organic sources of pollution and pollution status; invest identified potential sources of pollution and sample the soil to analysis. It turns out that the results of two identified historical pollution sources and pollutant concentration distribution are reliable. The results provided the basis for treatment of groundwater pollution.