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Abstract Background Ulcerative colitis (UC) is defined by persistent inflammatory processes within the gastrointestinal tract of uncertain etiology. Current therapeutic approaches are limited in their ability to address oxidative stress, inflammation, barrier function restoration, and modulation of gut microbiota in a coordinated manner to maintain intestinal homeostasis. Results This study involves the construction of a metal-phenolic nanozyme (Cur-Fe) through a ferric ion-mediated oxidative coupling of curcumin. Cur-Fe nanozyme exhibits superoxide dismutase (SOD)-like and •OH scavenging activities, demonstrating significant anti-inflammatory and anti-oxidant properties for maintaining intracellular redox balance in vitro. Drawing inspiration from Escherichia coli Nissle 1917 (EcN), a biomimetic Cur-Fe nanozyme (CF@EM) is subsequently developed by integrating Cur-Fe into the EcN membrane (EM) to improve the in vivo targeting ability and therapeutic effectiveness of the Cur-Fe nanozyme. When orally administered, CF@EM demonstrates a strong ability to colonize the inflamed colon and restore intestinal redox balance and barrier function in DSS-induced colitis models. Importantly, CF@EM influences the gut microbiome towards a beneficial state by enhancing bacterial diversity and shifting the compositional structure toward an anti-inflammatory phenotype. Furthermore, analysis of intestinal microbial metabolites supports the notion that the therapeutic efficacy of CF@EM is closely associated with bile acid metabolism. Conclusion Inspired by gut microbes, we have successfully synthesized a biomimetic Cur-Fe nanozyme with the ability to inhibit inflammation and restore intestinal homeostasis. Collectively, without appreciable systemic toxicity, this work provides an unprecedented opportunity for targeted oral nanomedicine in the treatment of ulcerative colitis.

Ulcerative colitis (UC) is characterized by chronic inflammatory processes of the intestinal tract of unknown origin. Current treatments lack understanding on how to effectively alleviate oxidative stress, relieve inflammation, as well as modulate gut microbiota for maintaining intestinal homeostasis synchronously. In this study, a novel drug delivery system based on a metal polyphenol network (MPN) was constructed via metal coordination between epigallocatechin gallate (EGCG) and Fe3+. Curcumin (Cur), an active polyphenolic compound, with distinguished anti-inflammatory activity was assembled and encapsulated into MPN to generate Cur-MPN. The obtained Cur-MPN could serve as a robust reactive oxygen species modulator by efficiently scavenging superoxide radical (O2•-) as well as hydroxyl radical (·OH). By hitchhiking yeast microcapsule (YM), Cur-MPN was then encapsulated into YM to obtain CM@YM. Our findings demonstrated that CM@YM was able to protect Cur-MPN to withstand the harsh gastrointestinal environment and enhance the targeting and retention abilities of the inflamed colon. When administered orally, CM@YM could alleviate DSS-induced colitis with protective and therapeutic effects by scavenging ROS, reducing pro-inflammatory cytokines, and regulating the polarization of macrophages to M1, thus restoring barrier function and maintaining intestinal homeostasis. Importantly, CM@YM also modulated the gut microbiome to a favorable state by improving bacterial diversity and transforming the compositional structure to an anti-inflammatory phenotype as well as increasing the content of short-chain fatty acids (SCFA) (such as acetic acid, propionic acid, and butyric acid). Collectively, with excellent biocompatibility, our findings indicate that synergistically regulating intestinal microenvironment will be a promising approach for UC.

With the emergence of wireless rechargeable sensor networks (WRSNs), the possibility of wirelessly recharging nodes using mobile charging vehicles (MCVs) has become a reality. However, existing approaches overlook the effective integration of node energy replenishment and mobile data collection processes. In this paper, we propose a joint energy replenishment and data collection scheme (D-JERDG) for WRSNs based on deep reinforcement learning. By capitalizing on the high mobility of unmanned aerial vehicles (UAVs), D-JERDG enables continuous visits to the cluster head nodes in each cluster, facilitating data collection and range-based charging. First, D-JERDG utilizes the K-means algorithm to partition the network into multiple clusters, and a cluster head selection algorithm is proposed based on an improved dynamic routing protocol, which elects cluster head nodes based on the remaining energy and geographical location of the cluster member nodes. Afterward, the simulated annealing (SA) algorithm determines the shortest flight path. Subsequently, the DRL model multiobjective deep deterministic policy gradient (MODDPG) is employed to control and optimize the UAV instantaneous heading and speed, effectively planning UAV hover points. By redesigning the reward function, joint optimization of multiple objectives such as node death rate, UAV throughput, and average flight energy consumption is achieved. Extensive simulation results show that the proposed D-JERDG achieves joint optimization of multiple objectives and exhibits significant advantages over the baseline in terms of throughput, time utilization, and charging cost, among other indicators.

Introduction: Dopamine is one of the most significant neurotransmitters and plays an important role in the management of cognitive functions such as learning, memory, and behavior. The disorder of dopamine is associated with many major mental diseases. It is necessary to develop selective methods for the detection of dopamine.Methods: In this work, carbon dots (CDs) were synthesized by a solvothermal route using glutathione, L-histidine, and formamide as sources.Results: Under light irradiation, The CDs convert dissolved oxygen to singlet oxygen (1O2), which could oxidize TMB. When reduced dopamine was present, it suppressed the catalysis of CDs, then the absorption of the CDs-coupled TMB complex at 652 nm was diminished. Furthermore, it was revealed that the surface groups including hydroxyl, amino, carbonyl, and carboxyl groups of CDs were related to their light-responsive catalytic activity by surface modification. In the range of 0.5-15 μM, the CDs could afford a LOD of 0.25 μM for dopamine detection with fine linearity, also showing good selectivity.Discussion: The results from fetal bovine serum indicated the good applicability of the CDs in the determination of dopamine.

Abstract Background Inflammatory bowel disease (IBD) is a chronic nonspecific disease with unknown etiology. Currently, the anti-inflammatory therapeutic approaches have achieved a certain extent of effects in terms of inflammation alleviation. Still, the final pathological outcome of intestinal fibrosis has not been effectively improved yet. Results In this study, dextran-coated cerium oxide (D-CeO2) nanozyme with superoxide dismutase (SOD) and catalase (CAT) activities was synthesized by chemical precipitation. Our results showed that D-CeO2 could efficiently scavenge reactive oxide species (ROS) as well as downregulate the pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and iNOS) to protect cells from H2O2-induced oxidative damage. Moreover, D-CeO2 could suppress the expression of fibrosis-related gene levels, such as α-SMA, and Collagen 1/3, demonstrating the anti-fibrotic effect. In both TBNS- and DSS-induced colitis models, oral administration of D-CeO2 in chitosan/alginate hydrogel alleviated intestinal inflammation, reduced colonic damage by scavenging ROS, and decreased inflammatory factor levels. Notably, our findings also suggested that D-CeO2 reduced fibrosis-related cytokine levels, predicting a contribution to alleviating colonic fibrosis. Meanwhile, D-CeO2 could also be employed as a CT contrast agent for noninvasive gastrointestinal tract (GIT) imaging. Conclusion We introduced cerium oxide nanozyme as a novel therapeutic approach with computed tomography (CT)-guided anti-inflammatory and anti-fibrotic therapy for the management of IBD. Collectively, without appreciable systemic toxicity, D-CeO2 held the promise of integrated applications for diagnosis and therapy, pioneering the exploration of nanozymes with ROS scavenging capacity in the anti-fibrotic treatment of IBD.

Intensification of biofuel production processes could play a critical role in boosting the economic and environmental features of the whole process. A novel bionic flow-induced peristaltic reactor with a high conversion rate is constructed to realize efficient biofuel production from high-concentration high-viscosity fluids. It is experimentally verified through biodiesel production from soybean oil. Experimental results show that the conversion efficiency is up to 89.9% at 10 s in the peristaltic reactor, which is 38.4% higher than that in the rigid tube reactor. Furthermore, a three-dimensional peristaltic model is conducted to understand the mechanism of heat and mass transfer enhancement. The simulation results show that an increase in peristaltic amplitude strengthens the mixing of the bionic peristaltic reactor by 92.5-100.8%. The temperature distribution in the bionic peristaltic reactor is more uniform than in the traditional rigid tube reactor. The results demonstrate that the conversion rate of soybean oil in the bionic flow-induced peristaltic reactor is 528.82% min-1, which is 17-60 times higher than other intensified reactors operating in either continuous or batch modes.

Small secreted peptides (SSPs) are important signals for cell-to-cell communication in plant, involved in a variety of growth and developmental processes, as well as responses to stresses. While a large number of SSPs have been identified and characterized in various plant species, little is known about SSPs in wheat, one of the most important cereal crops. In this study, 4,981 putative SSPs were identified on the wheat genome, among which 1,790 TaSSPs were grouped into 38 known SSP families. The result also suggested that a large number of the putaitive wheat SSPs, Cys-rich peptides in particular, remained to be characterized. Several TaSSP genes were found to encode multiple SSP domains, including CLE, HEVEIN and HAIRPININ domains, and two potentially novel TaSSP family DYY and CRP8CI were identified manually among unpredicted TaSSPs. Analysis on the transcriptomic data showed that a great proportion of TaSSPs were expressed in response to abiotic stresses. Exogenous application of the TaCEPID peptide encoded by TraesCS1D02G130700 enhanced the tolerance of wheat plants to drought and salinity, suggesting porential roles of SSPs in regulating stress responses in wheat.

The South-to-North Water Diversion Project (SNWDP) is a megaproject which has been constructed to alleviate imbalanced water resource distribution between northern and southern China. It encompasses three routes distributed in the east, central, and west of China, respectively. The central route (CR) of the SNWDP starts from the Danjiangkou Reservoir and ends in Beijing and Tianjin, running through Hubei, Henan, and Hebei Provinces; it has been in service since December 2014. For this type of megaproject, efficient and effective safety monitoring during its operation is highly challenging to the management department. Multitemporal interferometric synthetic aperture radar (MT-InSAR) has been widely applied in monitoring land deformation, especially in a wide area. However, its ability to show the deformation of one specific facility along the SNWD has not been deeply investigated. This study investigates the capability of MT-InSAR in monitoring the deformation of the canal and ancillary facilities along the SNWD-CR over Handan, Hebei Province, in China, using Sentinel-1, Radarsat-2, and TerraSAR-X datasets. Deformation rates from March 2015 to March 2016 are obtained by applying permanent scatterers (PS)-InSAR to these three SAR datasets. After combining the deformation rates derived by the three datasets, deformation along the SNWDP-CR is evaluated using a method encompassing median absolute deviation (MAD) calculation and heatmap. The evaluation result reveals that one part of the western embankment of the open canal is subsiding at up to 10 mm/year, which may be associated with overirrigation. Besides this location, the most dangerous areas assessed by the proposed method are related to ancillary facilities, mainly aqueducts and crossing-canal bridges.

NAC proteins constitute one of the largest transcription factor families and are involved in regulation of plant development and stress responses. Our previous transcriptome analyses of tobacco revealed a significant increase in the expression of NtNAC028 during leaf yellowing. In this study, we found that NtNAC028 was rapidly upregulated in response to high salinity, dehydration, and abscisic acid (ABA) stresses, suggesting a vital role of this gene in abiotic stress response. NtNAC028 loss-of-function tobacco plants generated via CRISPR-Cas9 showed delayed leaf senescence and increased tolerance to drought and salt stresses. Meanwhile NtNAC028 overexpression led to precocious leaf senescence and hypersensitivity to abiotic stresses in Arabidopsis, indicating that NtNAC028 functions as a positive regulator of natural leaf senescence and a negative regulator of stress tolerance. Furthermore, NtNAC028-overexpressing Arabidopsis plants showed lower antioxidant enzyme activities, higher reactive oxygen species (ROS), and H2O2 accumulation under high salinity, resulted in more severe oxidative damage after salt stress treatments. On the other hand, NtNAC028 mutation in tobacco resulted in upregulated expression of ROS-scavenging and abiotic stress-related genes, higher antioxidant enzyme activities, and enhanced tolerance against abiotic stresses, suggesting that NtNAC028 might act as a vital regulator for plant stress response likely by mediating ROS scavenging ability. Collectively, our results indicated that the NtNAC028 plays a key regulatory role in leaf senescence and response to multiple abiotic stresses.

Leaf senescence is a highly coordinated process and has a significant impact on agriculture. Plant peptides are known to act as important cell-to-cell communication signals that are involved in multiple biological processes such as development and stress responses. However, very limited number of peptides has been reported to be associated with leaf senescence. Here, we report the characterization of the INFLORESCENCE DEFICIENT IN ABSCISSION-LIKE6 (IDL6) peptide as a regulator of leaf senescence. The expression of IDL6 was up-regulated in senescing leaves. Exogenous application of synthetic IDL6 peptides accelerated the process of leaf senescence. The idl6 mutant plants showed delayed natural leaf senescence as well as senescence included by darkness, indicating a regulatory role of IDL6 peptides in leaf senescence. The role of IDL6 as a positive regulator of leaf senescence was further supported by the results of overexpression analysis and complementation test. Transcriptome analysis revealed differential expression of phytohormone-responsive genes in idl6 mutant plants. Further analysis indicated that altered expression of IDL6 led to changes in leaf senescence phenotypes induced by ABA and ethylene treatments. The results from this study suggest that the IDL6 peptide positively regulates leaf senescence in Arabidopsis thaliana.

The CLE family (CLAVATA3/embryo surrounding region-related), a class of small secreted proteins, play important roles in plant development and stress responses. Members of the CLE family have been characterized in a number of plant species, including Arabidopsis and rice. However, limited information is available about CLE peptides in tobacco (Nicotiana tabacum) and related Nicotiana species. Here we report the identification of 84 CLE family members in three Nicotiana species based on sequence similarity. The newly identified CLE members, including 41 from N. tabacum, 19 from N. sylvestris, and 24 from N. tomentosiformis, together with 32 CLEs from Arabidopsis and 52 CLEs from tomato, formed 9 subgroups in a phylogenic tree. The unbalanced distribution of the Nicotiana CLEs in the subgroups suggested potential preferential gene family expansion during evolution. Expression of the NtCLE genes was analyzed and a number of the NtCLEs showed induced expression upon abiotic stress treatments. Synthetic peptides of several NtCLEs, when applied to detached tobacco leaf discs, were able to increase plants’ tolerance to osmotic and salinity stresses, suggesting potential roles of CLE peptides in the stress responses of tobacco.

Abstract Background EPB41L1 gene (erythrocyte membrane protein band 4.1 like 1) encodes the protein 4.1N, a member of 4.1 family, playing a vital role in cell adhesion and migration, which is associated with the malignant progression of various human cancers. However, the expression and prognostic significance of EPB41L1 in kidney renal clear cell carcinoma (KIRC) remain to be investigated. Methods In this study, we collected the mRNA expression of EPB41L1 in KIRC through the Oncomine platform, and used the HPA database to perform the pathological tissue immunohistochemistry in patients. Then, the sub-groups and prognosis of KIRC were performed by UALCAN and GEPIA web-tool, respectively. Further, the mutation of EPB41L1 in KIRC was analyzed by c-Bioportal. The co-expression genes of EPB41L1 in KIRC were displayed from the LinkedOmics database, and function enrichment analysis was used by LinkFinder module in LinkedOmics. The function of EPB41L1 in cell adhesion and migration was confirmed by wound healing assay using 786-O cells in vitro. Co-expression gene network was constructed through the STRING database, and the MCODE plug-in of which was used to build the gene modules, both of them was visualized by Cytoscape software. Finally, the top modular genes in the same patient cohort were constructed through data mining in TCGA by using the UCSC Xena browser. Results The results indicated that EPB41L1 was down-expressed in KIRC, leading to a poor prognosis. Moreover, there is a mutation in the FERM domain of EPB41L1, but it has no significant effect on the prognosis of KIRC. The co-expressed genes of EPB41L1 were associated with cell adhesion and confirmed in vitro. Further analysis suggested that EPB41L1 and amyloid beta precursor protein (APP) were coordinated to regulated cancer cell adhesion, thereby increasing the incidence of cancer cell metastasis and tumor invasion. Conclusions In summary, EPB41L1 is constantly down-expressed in KIRC tissues, resulting a poor prognosis. Therefore, we suggest that it can be an effective biomarker for the diagnosis of KIRC.

Abstract Background Wheat straw, the most abundant lignocellulosic biomass in China, is rich in cellulose that can be hydrolyzed and then converted into biofuels, such as bioethanol and biohydrogen. However, the accessibility of cellulose and the enzyme activity are greatly reduced in the presence of lignin. This significantly increases the enzyme cost in the saccharification, which hampers industrial production of lignocellulosic biofuels. In this study, a laccase treatment system mediated by 1-hydroxybenzotriazole was employed to modify and degrade lignin to enhance subsequent enzymatic saccharification of wheat straw. A kinetic model considering enzyme adsorption on lignin was proposed to estimate the saccharification performance. Results Fourier transform infrared spectroscopy (FTIR) analyses showed that the peak intensity of lignin structure characteristics significantly changed after laccase-mediated system (LMS) treatment. 2D-nuclear magnetic resonance (NMR) analyses indicated that the aromatic ether bonds were cleaved and that guaiacyl (G) was oxidized after LMS treatment. X-ray diffraction (XRD) analyses suggested that the crystallinity of lignocellulose increased due to the partial degradation of lignin. As a result, the nonproductive adsorption of the enzyme on lignin was reduced by 28%, while the reducing sugar yield increased by 26%. A semi-empirical kinetic model was used to estimate the reducing sugar yield, the initial hydrolysis rate (K M ) and deactivation rate coefficient (α) of LMS-pretreated wheat straw were 0.157 (h−1) and 0.214 (h−1), respectively. The model showed high accuracy (predicting error

Aiming at the serious problem of agricultural tractor emission pollution, especially the limitation of nitrogen dioxide (NOx) and soot emissions, we took an agricultural diesel engine as the research object, and a diesel engine combustion chamber model was established for both simulated calculations and experimental verification analysis. The in-cylinder pressure and heat release obtained from the combustion chamber model simulation calculations were within 6% error of the experimental data. The overall trend of change was basically consistent. The established model can simulate the working conditions of the experimental engine relatively well. An artificial neural network (ANN) was also established as an agent model based on the indentation rate, tab depth, and combustion chamber depth as the input, and NOx and soot as the output. The decision coefficients of the ANN model were R2 = 0.95 and 0.93, with corresponding Mean Relative Error (MRE) values of 10.13 and 8.18%, respectively, which are within the generally required interval, indicating that the obtained ANN model has good adaptability and accuracy. On the basis of the general particle swarm optimization (PSO) algorithm, an improved PSO algorithm was proposed, in which the inertia factor is continuously adjusted with the help of the skip line function in the optimization process so that the inertia factor adapts to different rates and adjusts the magnitude of the corresponding values in different periods. The improved PSO algorithm was used to optimize the optimal input parameter matching of the agent model to form a new combustion chamber structure, which was imported into CONVERGE CFD software for emission simulation and comparison with the emissions of the original combustion chamber. It was found that the NOx reduction was about 1.21 g·(kW·h)−1, and the soot reduction was about 0.06 g·(kW·h)−1 with the new combustion chamber structure. The ANN + PSO optimization method proved to be effective in reducing the NOx and soot emissions of diesel engine pollutants, and it may also provide a reference and ideas for the design and development of relevant agricultural engine combustion chamber systems.

White-rot fungi is capable of producing extracellular enzymes that degrade lignin structure and facilitate biofuel production from lignocellulosic biomass wastes. However, fungal monocultures are constrained by low activities of the lignin-degrading enzyme system, leading to poor treatment efficiency and a long duration, which are not advantageous for large-scale applications. To improve enzyme production and enhance lignin degradation, a novel coculture system was proposed using the white-rot fungi Phanerochaete chrysosporium and Irpex lacteus CD2. The degradation efficiency of the alkali lignin by the fungal coculture was 26.4%, which was higher than that of the fungal monocultures. It was due to the production of lignin degrading enzymes was promoted in the liquid medium. Scanning electron microscopy, Fourier transform infrared, thermogravimetric and mercury porosimeter analyses results revealed that the alkali lignin treated with the fungal coculture had the largest porosity, and the degree of destruction of the alkali lignin structure by the fungal coculture was higher than that of the fungal monocultures. Meanwhile, the nonproductive adsorption of enzymes on alkali lignin was significantly reduced by 61.0% when the biomass was treated with the fungal coculture. As a result, the nonproductive adsorption was remarkably reduced, while it significantly improved the cellulase catalysis efficiency. These results demonstrated the synergistic effects of the fungal coculture for biomass treatment and provided a new approach for increasing lignin degradation while improving enzymatic catalysis and biofuel production through fungal coculture.

The refractive index of blood is a key biophysical parameter, which can reflect the physiological state. We measured the refractive index of whole blood and other components, such as serum, plasma, and hemoglobin, based on internal reflection by using a homemade apparatus in the spectral range of 400 to 750 nm. In addition to the hemoglobin solution, which has a Soret band about 420 nm and two Q-bands between 500 and 600 nm, the measurements of other samples are the normal dispersion curve. The results are approximated by the Cauchy equation and Sellmeier equation, and the correlation coefficients are more than 0.997. [ABSTRACT FROM AUTHOR]

This study determined the effect of dietary supplementation with selenium enriched yeast on egg selenium levels and egg production of North China laying hens. Healthy 60-week-old hens (n = 160) were randomly divided into four experimental groups and fed a basal diet supplemented with selenium enriched yeast at differing levels: 0.0 mg/kg (control group), 0.3 mg/kg (low-dose group), 0.6 mg/kg (medium-dose group) and 1.2 mg/kg (high-dose group). Each experimental group had four cohorts and each cohort had 10 hens. Experimental diets were fed for 28 d and daily egg production was recorded. Eggs were collected every seven days for determination of egg white, egg yolk and total egg selenium using hydride generationatomic fluorescence spectrometry. Selenium dietary supplementation significantly increased egg white, egg yolk and total egg levels, as well as daily egg production (P < 0.05). During the study, egg white, egg yolk and total egg selenium, as well as egg production, initially increased for low- and medium-dose groups and then plateaued. In contrast, these parameters initially increased and subsequently decreased for the high-dose group. Increasing levels of selenium supplementation proportionately increased egg white, egg yolk and total egg selenium levels, as well as egg production (P < 0.05). Dietary supplementation with selenium enriched yeast increases the egg white, egg yolk and total egg selenium levels, as well as egg production of North China hens (P < 0.05). This effect increased with increasing levels of supplementation with selenium enriched yeast. [ABSTRACT FROM AUTHOR]

A simple dual-port sum-difference beam antenna with high isolation is proposed. A T-shaped slot is utilized to achieve both sum-difference beam pattern and high port-isolation. The slot coupling feeding structure simplifies the feeding network and avoids complicated fabrication. The proposed antenna is simulated, fabricated and measured. Experimental validations confirm that the antenna has 10-dB impedance bandwidths of 10.2% (4.82-5.33 GHz) for the sum port and 2.0% (4.95-5.05 GHz) for the difference port, respectively. In addition, high port-isolation better than 50 dB is achieved covering a wide band from 4.0 GHz to 5.5 GHz. The proposed antenna exhibits a measured peak gain of 6.3 dBi for the sum beam and a null depth better than -26 dB for the difference beam. Measured results agree well with simulated ones. [ABSTRACT FROM AUTHOR]

We investigated the effect of thiazone, a widely used penetration enhancer, on in vitro porcine skin and muscle tissue by single-integrating sphere technique during optical clearing (OC) treatment. The results showed that thiazone induced an increase on the total transmittance of skin which led to a reduction in that of muscle in the spectral range from 400 to 800 nm. Small particles crystalized out from the thiazone-treated muscle were observed by microscopy imaging. With the help of x-ray diffraction measurement, we ascertained that the crystal was a single-crystal of thiazone, which mainly induced an increase of the scattering. Contrast transmittance measurements carried on the mixture of water, thizaone–propylene glycol solution showed that the free water in muscle could be the main reason for the thiazone crystallization. Therefore, during OC treatment of thiazone, the remarkable effect on skin and the noticeable inhibition effect on subcutaneous muscle tissue after penetrating into the skin should be considered. The experimental results provide such a reference for the choice of penetration enhancer. [ABSTRACT FROM AUTHOR]

A compact half-elliptic monopole antenna with triple notched-bands for UWB application, which is driven with differential feeding systems, is proposed. The basic antenna consists of two symmetrical half-elliptic patches and a modified ground plane. To reject the 5.5-GHz WLAN band effectively, two pairs of Ω-shaped strips are placed as parasitic elements close to the feedline. By introducing rectangular SRRs and an Ω-shaped slot on the radiators, the operating bands of 3.5-GHz WiMAX and 8-GHz ITU can be notched, respectively. Compared with conventional single-ended feed antennas, the proposed differential-fed antenna can achieve better polarization purity, especially in the high-frequency band. [ABSTRACT FROM AUTHOR]

The complex refractive index dispersion (CRID), which contains the information on the refractive index dispersion and extinction coefficient spectra, is an important optical parameter of biotissue. However, it is hard to perform the CRID measurement on biotissues due to their high scattering property. Continuous CRID measurement based on internal reflection (CCRIDM-IR) is introduced. By using a lab-made apparatus, internal reflectance spectra of biotissue samples at multiple incident angles were detected, from which the continuous CRIDs were calculated based on the Fresnel formula. Results showed that in 400- to 750-nm range, hemoglobin solution has complicated dispersion and extinction coefficient spectra, while other biotissues have normal dispersion properties, and their extinction coefficients do not vary much with different wavelengths. The normal dispersion can be accurately described by several coefficients of dispersion equations (Cauchy equation, Cornu equation, and Conrady equation). To our knowledge, this is the first time that the continuous CRID of scattering biotissue over a continuous spectral region is measured, and we hereby have proven that CCRIDM-IR is a good method for continuous CRID research of biotissue. [ABSTRACT FROM AUTHOR]

The physical changes of tissue are complicated to evaluate during optical clearing (OC) treatment. Monitoring the changes of optical parameters, including the complex refractive index (CRI), helps people better understand the OC process. From the imaginary part of CRI, we can deduce the extinction coefficient of tissue. Based on the total internal reflection method, the time-dependent CRI of porcine muscle during natural dehydration is well determined. Results show that the real RI increases continuously with the increase of dehydration time, whereas the extinction coefficient initially increases and then decreases. Finally, the extinction coefficient becomesmuch smaller than the initial value, which demonstrates that better tissue optical clarity is obtained. The change tendency of the extinction coefficient of tissue is used to qualitatively explain the dynamic change of transmittance of a natural dehydrated tissue. Consequently, CRI, especially its imaginary part, is a very useful optical parameter by which to evaluate the OC effect. [ABSTRACT FROM AUTHOR]

Traditionally, continuous refractive index dispersion (CRID) measurement of materials with scattering is hard to realize. In this paper, CRID measurement based on the derivative total reflection method (CRIDM-DTRM) is proposed to measure the CRID of both absorption and scattering materials. It effectively determined the CRID of K9 glass, concentrated milk, and 0.5% methyl red solution in the 400-750 nm range with the spectral resolution of about 0.259 nm. For the first time, CRID of a scattering material is measured. CRIDM-DTRM is a useful technique in the field of RID measurement, especially for biotissues and anomalous dispersion materials. [ABSTRACT FROM AUTHOR]

The refractive-index profile (RIP) of optical fibers is of fundamental significance in determining critical fiber properties. Here, we present the application of a two-dimensional (2-D) scanning focused refractive-index microscopy (SFRIM) to accurately obtain the 2-D RIP of a graded-index optical fiber. Some modifications are made to SFRIM for better 2-D measurement. Quantitative RIP of the fiber is obtained with derivative total reflection method. The refractive-index accuracy is 0.002. The measured result is in good agreement with theoretical expectation. This method is straightforward, simple, repeatable, and free from signal distortion. This technique is suitable for symmetric and asymmetric optical fibers. The results indicate that this technique can be applied to obtain the RIPs of a wide range of materials and has broad application prospect in many fields. [ABSTRACT FROM AUTHOR]

We report the dynamic refractive index (RI) change of tissue under a stepped compression load using a custom-built pressure apparatus. Angle-dependent reflectance profiles of biotissue samples are recorded, and the RI values are resolved using the derivative total reflection method. These results are relevant for understanding the mechanism of mechanical optical clearing, for investigating tissue dynamics under mechanical stimuli, and for other biomedical applications. [ABSTRACT FROM AUTHOR]

A novel approach for the generation of high-frequency microwave signals using a dual-wavelength single-longitudinal-mode fiber ring laser is proposed and demonstrated. In the proposed configuration, a dual-wavelength fiber Bragg grating (FBG) with two ultranarrow transmission bands in combination with a regular FBG is used to ensure single-longitudinal-mode operation of the fiber ring laser. A semiconductor optical amplifier is employed as the gain medium in the ring cavity. Since the two lasing wavelengths share the same gain cavity, the relative phase fluctuations between the two wavelengths are low and can be used to generate a low-phase-noise microwave signal without need of a microwave reference Source. Three dual-wavelength ultranarrow transmission-band FBGs with wavelength spacing of 0.148, 0.33, and 0.053 nm are respectively incorporated into the laser. Microwave signals at 18.68, 40.95, and 6.95 GHz are obtained by beating the dual wavelengths at a photodetector. The spectral width of the generated microwave signals as small as 80 kHz with a frequency stability better than 1 MHz in the free-running mode at room temperature is obtained. [ABSTRACT FROM AUTHOR]

A novel method for microwave signal generation using a rational harmonic actively mode-locked fiber ring laser is proposed and demonstrated. The microwave signal is generated by beating the actively mode-locked longitudinal modes from the rational mode-locked fiber ring laser at a photodetector. The phases of the longitudinal modes are phased locked, which ensures a generated microwave signal with very low phase noise. In the proposed approach, the generated microwave signal has a frequency a few times higher than the microwave drive signal. Therefore, only a low-frequency reference source and a low-speed modulator are required. A rational harmonic actively mode-locked fiber ring laser is experimentally demonstrated. With a microwave drive signal at 5.52 GHz, a microwave signal with a frequency that is four times the frequency of the microwave drive signal at 22.08 GHz is generated. The generated microwave signal is very stable with a spectral width of less than 1 Hz. [ABSTRACT FROM AUTHOR]

A theoretical and experimental study of a multiwavelength fiber-ring laser that incorporates a semiconductor optical amplifier (SOA) in the laser cavity as a phase modulator to suppress the homogeneous line broadening is presented. The analysis reveals that the phase shift introduced by the SOA-based phase modulator is more significant than that formed using a LiNbO3 phase modulator, which leads to a better suppression of the homogeneous line broadening. Multiwavelength lasing with small wavelength spacing and improved stability at room temperature is achieved. A fiber-ring laser based on the proposed approach is implemented. Stable multiwavelength operation with up to 26 wavelengths and wavelength spacing as small as 0.19 nm at room temperature is demonstrated. [ABSTRACT FROM PUBLISHER]

Non-homogenous material such as solid composite materials examination using refractive index-sensing remains a challenge for researchers. A derivative total reflection method for simultaneous measurement of the refractive indices of various components of a non-homogeneous solid was developed. Only a measurement of the reflectance from the surface of composite sample is necessary. In our experiments, simulation samples, porcine tissue, and Rosso Levanto marble samples were measured to verify proposed method. [ABSTRACT FROM AUTHOR]

A novel single-longitudinal-mode (SLM) fiber ring laser that incorporates an equivalent phase-shifted fiber Bragg grating acting as an ultra-narrow bandpass filter in the laser cavity is proposed. The equivalent phase-shifted fiber Bragg grating has an ultra-narrow transmission bandwidth which ensures an SLM lasing. Stable SLM operation without mode hopping is demonstrated. [ABSTRACT FROM PUBLISHER]

A novel room-temperature multiwavelength erbium-doped fiber (EDF) laser is demonstrated. Stable multiwavelength lasing at room temperature is realized by incorporating a semiconductor optical amplifier (SOA)-based phase modulator in the laser cavity. The SOA is biased below the transparent point with a sinusoidal signal applied to achieve phase modulation, to suppress the homogenous line broadening of the EDF. Stable multiwavelength lasing with wavelengths up to 26 and wavelength spacing as small as 0.19 nm is demonstrated at room temperature. [ABSTRACT FROM PUBLISHER]