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Early detection of skin pathologies with current clinical diagnostic tools is challenging, particularly when there are no visible colour changes or morphological cues present on the skin. In this study, we present a terahertz (THz) imaging technology based on a narrow band quantum cascade laser (QCL) at 2.8 THz for human skin pathology detection with diffraction limited spatial resolution. THz imaging was conducted for three different groups of unstained human skin samples (benign naevus, dysplastic naevus, and melanoma) and compared to the corresponding traditional histopathologic stained images. The minimum thickness of dehydrated human skin that can provide THz contrast was determined to be 50 µm, which is approximately one half-wavelength of the THz wave used. The THz images from different types of 50 µm-thick skin samples were well correlated with the histological findings. The per-sample locations of pathology vs healthy skin can be separated from the density distribution of the corresponding pixels in the THz amplitude-phase map. The possible THz contrast mechanisms relating to the origin of image contrast in addition to water content were analyzed from these dehydrated samples. Our findings suggest that THz imaging could provide a feasible imaging modality for skin cancer detection that is beyond the visible.
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OBJECTIVE To investigate the protective effects and mechanism of ziyuglycoside Ⅰ on acute lung injury in sepsis rats based on network pharmacology， and conduct experimental verification. METHODS The network pharmacology was used to predict the potential target of ziyuglycoside Ⅰ in the treatment of acute lung injury following sepsis. The rat model of sepsis was reproduced by cecum ligation and puncture for experimental verification. Totally 192 SD rats were randomly divided into the sham operation group （Sham group）， sepsis group （Sep group）， conventional therapy group （CT group） and ziyuglycoside Ⅰ group （Zg Ⅰ group）， respectively. Sham group and Sep group were given sterile normal saline， and CT group and ZgⅠ group were given relevant volume of Ringer’s solution and ziyuglycoside Ⅰ. The arterial blood gas， serum inflammatory factors， lung wet/dry mass ratio， pathological changes of lung tissue， pulmonary vascular permeability， the expressions of pulmonary vein tight junction protein 1 （ZO-1） and vascular endothelial cadherin （VE-cadherin） protein and 72-hour survival were observed in each group. RESULTS Results of network pharmacology showed that there were 47 potential targets of ziyuglycoside Ⅰ in the treatment of sepsis. The results of gene ontology function enrichment analysis and Kyoto encyclopedia of genes and genomes pathway enrichment analysis showed that the mechanism could 598486924@qq.com be correlated with biological processes such as positive regulation of reactive oxygen species metabolism， wound healing， regulation of endothelial cell proliferation， cell activation， blood vessel development， response to oxidative stress， etc.， and with signaling pathway such as apoptosis， tight junction， HIF-1 signaling pathway， etc. The results of experimental verification showed that compared with Sham group， pH value and the level of partial arterial oxygen pressure were decreased significantly in Sep group （P＜0.05）， while the level of partial pressure of carbon dioxide， serum levels of tumor necrosis factor α， interleukin 6 were increased significantly （P＜0.05）； the ratio of lung wet/dry mass was increased significantly （P＜0.05）； the protein expressions of ZO-1 and VE-cadherin were decreased significantly （P＜0.05）； 72 h survival rate decreased，the survival time was significantly shortened （P＜0.05）； the results of pathological observation of lung tissue showed that the rats’ alveoli were extensively ruptured， the alveolar wall was thickened and accompanied with edema， and there was obvious inflammatory cell infiltration； the results of pulmonary vascular permeability observation showed that the lung surface of rats was dark， with a large amount of Evans blue exudation， and the left lower lung was obviously dark blue. Compared with Sep group， the levels of above indexes almost were reversed significantly in CT group and ZgⅠ group （P＜0.05）； the lung histopathology and pulmonary vascular permeability were significantly improved， and the recovery degree of ZgⅠ group was greater than that of CT group， which was close to the results of Sham group. CONCLUSIONS Ziyuglycoside Ⅰ can significantly reduce inflammatory reaction and acute lung injury in septic rats， which is related to vascular function and tight junction signal pathway.
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The typical modal characteristics arising during laser feedback interferometry (LFI) in multi-mode terahertz (THz) quantum cascade lasers (QCLs) are investigated in this work. To this end, a set of multi-mode reduced rate equations with gain saturation for a general Fabry-Pérot multi-mode THz QCL under optical feedback is developed. Depending on gain bandwidth of the laser and optical feedback level, three different operating regimes are identified, namely a single-mode regime, a multi-mode regime, and a tuneable-mode regime. When the laser operates in the single-mode and multi-mode regimes, the self-mixing signal amplitude (peak to peak value of the self-mixing fringes) is proportional to the feedback coupling rate at each mode frequency. However, this rule no longer holds when the laser enters into the tuneable-mode regime, in which the feedback level becomes sufficiently strong (the boundary value of the feedback level depends on the gain bandwidth). The mapping of the identified feedback regimes of the multi-mode THz QCL in the space of the gain bandwidth and feedback level is investigated. In addition, the dependence of the aforementioned mapping of these three regimes on the linewidth enhancement factor of the laser is also explored, which provides a systematic picture of the potential of LFI in multi-mode THz QCLs for spectroscopic sensing applications.
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We propose a self-consistent method for the analysis of granular materials at terahertz (THz) frequencies using a quantum cascade laser. The method is designed for signals acquired from a laser feedback interferometer, and applied to non-contact reflection-mode sensing. Our technique is demonstrated using three plastic explosives, achieving good agreement with reference measurements obtained by THz time-domain spectroscopy in transmission geometry. The technique described in this study is readily scalable: replacing a single laser with a small laser array, with individual lasers operating at different frequencies will enable unambiguous identification of select materials. This paves the way towards non-contact, reflection-mode analysis and identification of granular materials at THz frequencies using quantum cascade lasers.
