PFC/M1 activation and excitability: a longitudinal cohort study on fatigue symptoms in healthcare workers post-COVID-19.

BACKGROUND: Fatigue is one of the most common neurological symptoms reported post coronavirus disease 2019 (COVID-19) infection. In order to establish effective early intervention strategies, more emphasis should be placed on the correlation between fatigue and cortical neurophysiological changes, especially in healthcare workers, who are at a heightened risk of COVID-19 infection. METHODS: A prospective cohort study was conducted involving 29 COVID-19 medical workers and 24 healthy controls. The assessment included fatigue, sleep and health quality, psychological status, and physical capacity. Functional near-infrared spectroscopy (fNIRS) was employed to detect activation of brain regions. Bilateral primary motor cortex (M1) excitabilities were measured using single- and paired-pulse transcranial magnetic stimulation. Outcomes were assessed at 1, 3, and 6 months into the disease course. RESULTS: At 1-month post-COVID-19 infection, 37.9% of patients experienced severe fatigue symptoms, dropping to 10.3% at 3 months. Interestingly, the remarkable decreased activation/excitability of bilateral prefrontal lobe (PFC) and M1 were closely linked to fatigue symptoms after COVID-19. Notably, greater increase in M1 region excitability correlated with more significant fatigue improvement. Re-infected patients exhibited lower levels of brain activation and excitability compared to single-infection patients. CONCLUSIONS: Both single infection and reinfection of COVID-19 lead to decreased activation and excitability of the PFC and M1. The degree of excitability improvement in the M1 region correlates with a greater recovery in fatigue. Based on these findings, targeted interventions to enhance and regulate the excitability of M1 may represent a novel strategy for COVID-19 early rehabilitation. TRIAL REGISTRATION: The Ethics Review Committee of Xijing Hospital, No. KY20232051-F-1; www.chictr.org.cn , ChiCTR2300068444.

Correlation of bilateral M1 hand area excitability and overall functional recovery after spinal cord injury: protocol for a prospective cohort study.

BACKGROUND: After spinal cord injury (SCI), a large number of survivors suffer from severe motor dysfunction (MD). Although the injury site is in the spinal cord, excitability significantly decreases in the primary motor cortex (M1), especially in the lower extremity (LE) area. Unfortunately, M1 LE area-targeted repetitive transcranial magnetic stimulation (rTMS) has not achieved significant motor improvement in individuals with SCI. A recent study reported that the M1 hand area in individuals with SCl contains a compositional code (the movement-coding component of neural activity) that links matching movements from the upper extremities (UE) and the LE. However, the correlation between bilateral M1 hand area excitability and overall functional recovery is unknown. OBJECTIVE: To clarify the changes in the excitability of the bilateral M1 hand area after SCI and its correlation with motor recovery, we aim to specify the therapeutic parameters of rTMS for SCI motor rehabilitation. METHODS: This study is a 12-month prospective cohort study. The neurophysiological and overall functional status of the participants will be assessed. The primary outcomes included single-pulse and paired-pulse TMS. The second outcome included functional near-infrared spectroscopy (fNIRS) measurements. Overall functional status included total motor score, modified Ashworth scale score, ASIA Impairment Scale grade, spinal cord independence measure and modified Barthel index. The data will be recorded for individuals with SCI at disease durations of 1 month, 2 months, 4 months, 6 months and 12 months. The matched healthy controls will be measured during the same period of time after recruitment. DISCUSSION: The present study is the first to analyze the role of bilateral M1 hand area excitability changes in the evaluation and prediction of overall functional recovery (including motor function and activities of daily living) after SCI, which will further expand the traditional theory of the predominant role of M1, optimize the current rTMS treatment, and explore the brain-computer interface design for individuals with SCI. TRIAL REGISTRATION NUMBER: ChiCTR2300068831.

Controlling Charge Transport in 2D Conductive MOFs─The Role of Nitrogen-Rich Ligands and Chemical Functionality.

Two-dimensional electrically conducting metal-organic frameworks (2D-e-MOFs) have emerged as a class of highly promising functional materials for a wide range of applications. However, despite the significant recent advances in 2D-e-MOFs, developing systems that can be postsynthetically chemically functionalized, while also allowing fine-tuning of the transport properties, remains challenging. Herein, we report two isostructural 2D-e-MOFs: Ni3(HITAT)2 and Ni3(HITBim)2 based on two new 3-fold symmetric ligands: 2,3,7,8,12,13-hexaaminotriazatruxene (HATAT) and 2,3,8,9,14,15-hexaaminotribenzimidazole (HATBim), respectively, with reactive sites for postfunctionalization. Ni3(HITAT)2 and Ni3(HITBim)2 exhibit temperature-activated charge transport, with bulk conductivity values of 44 and 0.5 mS cm-1, respectively. Density functional theory analysis attributes the difference to disparities in the electron density distribution within the parent ligands: nitrogen-rich HATBim exhibits localized electron density and a notably lower lowest unoccupied molecular orbital (LUMO) energy relative to HATAT. Precise amounts of methanesulfonyl groups are covalently bonded to the N-H indole moiety within the Ni3(HITAT)2 framework, modulating the electrical conductivity by a factor of ∼20. These results provide a blueprint for the design of porous functional materials with tunable chemical functionality and electrical response.

Ultrasensitive detection of SARS-CoV-2 S protein with aptamers biosensor based on surface-enhanced Raman scattering.

A rapid and accurate diagnostic modality is essential to prevent the spread of SARS-CoV-2. In this study, we proposed a SARS-CoV-2 detection sensor based on surface-enhanced Raman scattering (SERS) to achieve rapid and ultrasensitive detection. The sensor utilized spike protein deoxyribonucleic acid aptamers with strong affinity as the recognition entity to achieve high specificity. The spherical cocktail aptamers-gold nanoparticles (SCAP) SERS substrate was used as the base and Au nanoparticles modified with the Raman reporter molecule that resonates with the excitation light and spike protein aptamers were used as the SERS nanoprobe. The SCAP substrate and SERS nanoprobes were used to target and capture the SARS-CoV-2 S protein to form a sandwich structure on the Au film substrate, which can generate ultra-strong "hot spots" to achieve ultrasensitive detection. Analysis of SARS-CoV-2 S protein was performed by monitoring changes in SERS peak intensity on a SCAP SERS substrate-based detection platform. This assay detects S protein with a LOD of less than 0.7 fg mL-1 and pseudovirus as low as 0.8 TU mL-1 in about 12 min. The results of the simulated oropharyngeal swab system in this study indicated the possibility of it being used for clinical detection, providing a potential option for rapid and accurate diagnosis and more effective control of SARS-CoV-2 transmission.

Bimetallic Anionic Organic Frameworks with Solid-State Cation Conduction for Charge Storage Applications.

A new phosphonate-based anionic bimetallic organic framework, with the general formula of A4 -Zn-DOBDP (wherein A is Li+ or Na+ , and DOBDP6- is the 2,5-dioxido-1,4-benzenediphosphate ligand) is prepared and characterized for energy storage applications. With four alkali cations per formula unit, the A4 -Zn-DOBDP MOF is found to be the first example of non-solvated cation conducting MOF with measured conductivities of 5.4×10-8  S cm-1 and 3.4×10-8  S cm-1 for Li4 - and Na4 - phases, indicating phase and composition effects of Li+ and Na+ shuttling through the channels. Three orders of magnitude increase in ionic conductivity is further attained upon solvation with propylene carbonate, placing this system among the best MOF ionic conductors at room temperature. As positive electrode material, Li4 -Zn-DOBDP delivers a specific capacity of 140 mAh g-1 at a high average discharge potential of 3.2 V (vs. Li+ /Li) with 90 % of capacity retention over 100 cycles. The significance of this research extends from the development of a new family of electroactive phosphonate-based MOFs with inherent ionic conductivity and reversible cation storage, to providing elementary insights into the development of highly sought yet still evasive MOFs with mixed-ion and electron conduction for energy storage applications.

Dual-linear chirp microwave signal generation by using single-beam injection to a DFB semiconductor laser and optical heterodyne technique.

Based on a single-beam injection distributed feedback semiconductor laser (DFB-SL) combining with optical heterodyne, a photonic scheme for generating dual-linear chirp microwave (dual-LCM) signal with identical or complementary chirp is proposed and experimentally demonstrated. For such a scheme, a continuous-wave (CW) light with a frequency of finj is split into two parts. One part is passing through a Mach-Zehnder modulator (MZM) driven by a modified sawtooth signal, and then its intensity varies with time as a sawtooth wave. Such a light is injected to a DFB-SL for generating a single linearly chirped microwave (single-LCM) signal. The other part of the CW light with frequency of finj is sent to a phase modulator (PM) driven by a sinusoidal signal, and one of higher-order sidebands is selected by a tunable optical filter and taken as the referenced light. Through heterodyning the referenced light with the single-LCM signal, a dual-LCM signal with identical (or complementary) chirp can be obtained. The experimental results demonstrate that, by adjusting the injection parameters and the frequency of the sinusoidal signal loaded on the PM, the central frequency of the generated dual-LCM signal can be widely tuned. For the period of the sawtooth signal at 10 µs, the bandwidth for each frequency band included in the generated dual-LCM signal is 19.36 GHz under identical chirp and 16.98 GHz under complementary chirp, respectively. Correspondingly, the time bandwidth product (TBWP) for each frequency band can reach 1.936 × 105 under identical chirp and 1.698 × 105 under complementary chirp, respectively.

A cascade Fermat spiral microfluidic mixer chip for accurate detection and logic discrimination of cancer cells.

Since cancer has emerged as one of the most serious threats to human health, the highly sensitive determination of cancer cells is of significant importance to improve the accuracy of early clinical diagnosis. In our investigation, a novel cascade Fermat spiral microfluidic mixer chip (CFSMMC) combined with fluorescence sensors as a point-of-care (POC) testing system is successfully fabricated to detect and differentiate cancer cells (MCF-7) from normal cells with excellent sensitivity and selectivity. Here, copper ions (Cu2+) with peroxidase properties can catalyze the oxidation of the non-fluorescent substrate Amplex Red (AR) to the highly fluorescent resorufin (ox-AR) in the presence of hydrogen peroxide (H2O2). Subsequently, thanks to the quenching response of AS1411-AuNPs to ox-AR in the microchannel and the binding of AS1411 to nucleolin on the surface of cancer cells, a CFSMMC-based POC system is established for the highly sensitive detection and identification of human breast cancer cells in a "turn on" manner. The change in fluorescence intensity is linearly related to the concentration of MCF-7, ranging from 102 to 107 cells per mL with a limit of detection (LOD) as low as 17 cells per mL. Interestingly, the cascaded AND logic gate is integrated with CFSMMC for the first time to distinguish cancer cells from normal cells under the control of logic functions, which exhibits great potential in the development of one-step rapid and intelligent detection and logic discrimination.

A Complement Method for Magnetic Data Based on TCN-SE Model.

The magnetometer is a vital measurement component for attitude measurement of near-Earth satellites and autonomous magnetic navigation, and monitoring health is significant. However, due to the compact structure of the microsatellites, the stray magnetic changes caused by the complex working conditions of each system will inevitably interfere with the magnetometer measurement. In addition, due to the limited capacity of the satellite-ground measurement channels and the telemetry errors caused by the harsh space environment, the magnetic data collected by the ground station are partially missing. Therefore, reconstructing the telemetry data on the ground has become one of the key technologies for establishing a high-precision magnetometer twin model. In this paper, firstly, the stray magnetic interference is eliminated by correcting the installation matrix for different working conditions. Then, the autocorrelation characteristics of the residuals are analyzed, and the TCN-SE (temporal convolutional network-squeeze and excitation) network with long-term memory is designed to model and extrapolate the historical residual data. In addition, MAE (mean absolute error) is used to analyze the data without missing at the corresponding time in the forecast period and decreases to 74.63 nT. The above steps realize the accurate mapping from the simulation values to the actual values, thereby achieving the reconstruction of missing data and establishing a solid foundation for the judgment of the health state of the magnetometer.

High-Performance Lithium-Oxygen Batteries Using a Urea-Based Electrolyte with Kinetically Favorable One-Electron Li2 O2 Oxidation Pathways.

Glymes are the most widely used electrolyte solvents in lithium-oxygen batteries (LOBs) due to their relatively high stability. However, their associated LOBs have long been plagued by large charge overpotential, which is closely related to the sluggish two-electron Li2 O2 oxidation mechanism. Here, we report a new electrolyte solvent-1,1,3,3-tetramethylurea (TMU) for LOBs with high performance and an alternative mechanism, where a kinetically favorable one-electron Li2 O2 oxidation pathway can happen in the urea electrolyte system, thus leading to a much lower charge overpotential (≈0.51 V) compared to the tetraglyme-based LOBs (≈1.27 V). Besides, TMU also exhibits good stability since it does not contain any α-hydrogen atoms that are vulnerable to be attacked by superoxide species, thus suppressing the hydrogen abstraction side reactions. Consequently, the TMU-based LOBs can stably work for more than 135 cycles, which is four times that of the tetraglyme-based LOBs (≈28 cycles).

Bacteria-Triggered Multifunctional Hydrogel for Localized Chemodynamic and Low-Temperature Photothermal Sterilization.

Pathogenic infections seriously threaten public health and have been considered as one of the most critical challenges in clinical therapy. Construction of a safe and efficient photothermal antibacterial platform is a promising strategy for treatment of bacterial infections. Considering that high temperature does harm to the normal tissues and cells, herein, a bacteria-triggered multifunctional hydrogel is constructed for low-temperature photothermal sterilization with high efficiency by integrating localized chemodynamic therapy (L-CDT). The hydrogel is constructed by incorporating copper sulfide nanoparticles (CuSNPs ) with photothermal profile into the network of hyaluronic acid (HA) and Fe3+ -EDTA complexes, named as CHFH (CuSNPs -HA-Fe3+ -EDTA hydrogel). Bacteria can be accumulated on the surface of CHFH, which secretes hyaluronidase to decompose the HA and release Fe3+ . The Fe3+ is reduced into Fe2+ in microenvironment of bacteria to trigger Fenton reaction. The generated hydroxyl radicals result in sterilization based on L-CDT within short range. By integrating with photothermal property of CuSNPs , low-temperature photothermal therapy (LT-PTT) for sterilization is realized, which improves the antibacterial efficiency while minimizes damage to normal tissues. The CHFH is further used to prepare Band aid which effectively promotes the Staphylococcus aureus-infected wound healing process in vivo, confirming the great potential for clinical application.

A Highly Reversible Lithium Metal Anode by Constructing Lithiophilic Bi-Nanosheets.

As a favorable candidate for the next-generation anode materials, metallic lithium is faced with two crucial problems: uncontrollable lithium plating/stripping process and huge volume expansion during cycling. Herein, a 3D lithiophilic skeleton modified with nanoscale Bi sheets (Ni@Bi Foam, i.e., NBF) through one-step facile substitution reaction is constructed. Benefiting from the nanoscale modification, smooth and dense lithiophilic Li3 Bi layer is in situ formed, which improves the uniform deposition of Li subsequently. Meanwhile, the 3D structure inhibits the growth of Li dendrites effectively by reducing local areal current density. Consequently, the NBF exhibits outstanding cycling stability with a high average Coulombic efficiency of 98.46% at 1 mA cm-2 with 1 mAh cm-2 (>500 cycles). Symmetrical cell with NBF exhibits a high reversibility at 1 mA cm-2 with 1 mAh cm-2 (>2000 h). Moreover, superior long-term cycling and rate performance of NBF@Li anode are also acquired when assembled with high areal loading of LiFePO4 (10.1 mg cm-2 ) cathode (Negative/Positive ratio: 2.91). Even in anode-free metal lithium batteries, NBF has higher capacity during cycling compared with NF. To conclude, NBF shows excellent electrochemical performance and provides an idea of facile preparation method which can be extend to other metal batteries.

High-quality frequency-modulated continuous-wave generation based on a semiconductor laser subject to cascade-modulated optical injection.

Frequency-modulated continuous-wave (FMCW) can be acquired by using a distributed feedback semiconductor laser (DFB-SL) operating at period-one (P1) oscillation under an optical injection modulated by a Mach-Zehnder modulator (MZM). In this work, through introducing another MZM to establish cascade-modulated optical injection, an improved photonic scheme for generating high-quality FMCW is proposed and experimentally demonstrated. The experimental results indicate that, under appropriate injection parameters, the central frequency of the generated FMCW is widely tunable, and the bandwidth is larger than that obtained under a single MZM modulation. Further introducing optical feedback for suppressing the phase noise, the frequency comb contrast of the generated FMCW can be improved obviously.

Common and distinct brain functional alterations in pharmacotherapy treatment-naïve female borderline personality disorder patients with and without auditory verbal hallucinations: a pilot study.

Auditory verbal hallucinations (AVHs) are experienced by approximately 25% of patients with borderline personality disorder (BPD). Despite the high incidence, the pathological features of AVH in BPD remain unclear. This study aimed to investigate whole-brain functional connectivity (FC), as measured by functional connectivity density (FCD), and its relationship with AVH in BPD. 65 pharmacotherapy treatment-naïve female BPD patients (30 with AVH and 35 without AVH), and 35 female healthy controls were investigated. Functional magnetic resonance imaging (fMRI) data were collected to assess whole-brain FC and functional connectivity density mapping (FCDM) was applied to the fMRI data to compute FCD features. Compared to the healthy controls, both BPD groups (BPD-AVH and BPD without AVH) exhibited significantly higher gFCD values in the bilateral prefrontal lobe, bilateral orbital lobule, and bilateral insula, and significantly lower gFCD values in the SMA, right anterior temporal lobule, and the ACC. These altered regions were significantly associated with AVH in the BPD subjects. Moreover, higher gFCD values were observed in the left posterior temporal lobule and posterior frontal lobule. Aberrant alterations also emerged in the left posterior temporal lobule and posterior frontal lobule, mainly in Broca and Wernicke regions. Nevertheless, there was no significant correlation between gFCD values and the severity of AVH as measured by the AVH scores. In summary, we have identified aberrations in the FC and brain metabolism of the aforementioned neural circuits/networks, which may provide new insights into BPD-AVH and facilitate the development of therapeutic approaches for treating AVH in BPD patients.

A typical antipsychotic treatment induced gradually expanding white matter alterations in healthy individuals with persistent auditory verbal hallucinations-an artificially controlled pilot study.

OBJECTIVE: The aim of this study was to explore the effects of atypical antipsychotics (AaPs) on brain white matter (WM) tracts in healthy individuals with auditory verbal hallucinations (Hi-AVHs). METHODS: We analyzed neuroimaging, AVH symptoms, and cognitive assessment data obtained from 39 Hi-AVHs who reported being distressed by persistent AVHs and volunteered to receive AaP treatment. We used tract-based spatial statistics (TBSS) and t tests to explore AaP pharmacotherapy effects on AVH symptoms and brain WM alterations in Hi-AVH subjects. RESULTS: TBSS and t tests revealed WM alterations after AaP treatment, relative to pretreatment observations. Although AaPs alleviated AVH symptoms, WM alterations in these subjects expanded over 8 months of AaP treatment, encompassing most major WM tracts by the end of the observation period, including the corpus callosum, arcuate fasciculus, cortico-spinal tracts, anterior commissure, and posterior commissure. CONCLUSIONS: The worsening of AaP-associated WM alterations observed in this study suggest that AaPs may not be a good choice for the treatment of Hi-AVHs despite their ability to alleviate AVHs.

A SLIC-DBSCAN Based Algorithm for Extracting Effective Sky Region from a Single Star Image.

The star tracker is widely used for high-accuracy missions due to its high accuracy position high autonomy and low power consumption. On the other hand, the ability of interference suppression of the star tracker has always been a hot issue of concern. A SLIC-DBSCAN-based algorithm for extracting effective information from a single image with strong interference has been developed in this paper to remove interferences. Firstly, the restricted LC (luminance-based contrast) transformation is utilized to enhance the contrast between background noise and the large-area interference. Then, SLIC (the simple linear iterative clustering) algorithm is adopted to segment the saliency map and in this process, optimized parameters are harnessed. Finally, from these segments, features are extracted and superpixels with similar features are combined by using DBSCAN (density-based spatial clustering of applications with noise). The proposed algorithm is proved effective by successfully removing large-area interference and extracting star spots from the sky region of the real star image.

Comparison studies of excitonic properties and multiphoton absorption of near-infrared-I-emitting Cu-doped InP and InP/ZnSe nanocrystals.

Cu-doped InP (Cu:InP) and InP/ZnSe nanocrystals (NCs) with near-infrared-I (NIR-I) emission were prepared and characterized. Femtosecond transient absorption spectra revealed that the epitaxial growth of a ZnSe diffusion barrier onto the Cu:InP core can amplify its exciton-dopant coupling strength, with the energy transfer times of $\sim{220}\;{\rm ps}$∼220ps for Cu:InP NCs and $\sim{183}\;{\rm ps}$∼183ps for Cu:InP/ZnSe NCs. Importantly, the Cu:InP/ZnSe NCs exhibit much larger two- and three-photon absorption cross sections, reaching $\sim{10162}$∼10162 GM at 1030 nm and $\sim{1.06} \times {{10}^{ - 77}}\;{{\rm cm}^6}\,{{\rm s}^2}\,{{\rm photon}^{ - 2}}$∼1.06×10-77cm6s2photon-2 at 1600 nm, compared with Cu:InP NCs.

Numerical simulations on narrow-linewidth photonic microwave generation based on a QD laser simultaneously subject to optical injection and optical feedback.

Based on a three-level model for quantum dot (QD) lasers, the characteristics of the photonic microwave generated by a QD laser simultaneously subject to optical injection and optical feedback are numerically investigated. First, the performance of the microwave signal generated by an optical injected QD laser operating at period one state are analyzed, and the mappings of the frequency and intensity of the generated microwave in the parameter space of the frequency detuning and injection strength are given, which are roughly similar to those reported experimentally. Next, an optical feedback loop is further introduced to the optically injected QD laser for compressing the linewidth of the microwave signal, and the results demonstrate that the linewidth of the generated microwave can be reduced by at least 1 order of magnitude under suitable feedback parameters. Finally, the effect of the linewidth enhancement factor on the generated microwave signal is analyzed.

Smartphone-based enzyme-free fluorescence sensing of organophosphate DDVP.

A novel fluorescence strategy based on the outstanding catalytic capability of CuS nanoparticles (CuSNPs) has been developed for highly sensitive and specific determination of o,o-dimethyl-o-2,2-dichlorovinyl phosphate (DDVP) under enzyme-free and hydrogen peroxide (H2O2)-free conditions. In the presence of DDVP, CuSNPs can catalyze non-fluorescence substratum of Amplex red (AR) into resorufin, which exhibits fluorescence emission at 584 nm under excitation at 540 nm. The sensing system exhibits outstanding specificity and only responds to DDVP and no other organophosphorus pesticides (OPs). A wide linear range is obtained from 0.0001 to 0.1 µg/mL, and the limit of detection (LOD) is 0.1 ng/mL. Furthermore, paper-based test strips have been constructed for visual detection of DDVP under ultraviolet light irradiation. By integrating a smartphone installed with Color Picker APP, point-of-care detection with quantitative determination is realized, demonstrating substantial potential applications of the as-developed assay for in situ detection. Graphical abstract.

Parallel Three-Branch Correlation Filters for Complex Marine Environmental Object Tracking Based on a Confidence Mechanism.

Marine object tracking is critical for search and rescue activities in the complex marine environment. However, the complex marine environment poses a huge challenge to the effect of tracking, such as the variability of light, the impact of sea waves, the occlusion of other ships, etc. Under these complex marine environmental factors, how to design an efficient dynamic visual tracker to make the results accurate, real time and robust is particularly important. The parallel three-branch correlation filters for complex marine environmental object tracking based on a confidence mechanism is proposed by us. The proposed tracker first detects the appearance change and position change of the object by constructing parallel three-branch correlation filters, which enhances the robustness of the correlation filter model. Through the weighted fusion of response maps, the center position of the object is accurately located. Secondly, the Gaussian-triangle joint distribution is used to replace the original Gaussian distribution in the training phase. Finally, a verification mechanism of confidence metric is embedded in the filter update section to analyze the tracking effect of the current frame, and to update the filter sample from verification result. Thus, a more accurate correlation filter is trained to prevent model drift and achieve a good tracking effect. We found that the effect of various interferences on the filter is effectively reduced by comparing with other trackers. The experiments prove that the proposed tracker can play an outstanding role in the complex marine environment.

Frequency-modulated continuous-wave generation based on an optically injected semiconductor laser with optical feedback stabilization.

Based on the period-one (P1) dynamics of an optically injected semiconductor laser (SL), a photonic scheme enabling the generation of a tunable high-quality frequency-modulated continuous-wave (FMCW) signal is investigated experimentally. Under a modulated optical injection, the laser is driven into P1 oscillation with a modulated microwave frequency. In this work, optical feedback is also introduced to further reduce the microwave phase noise. The experimental results show that the central frequency of the generated FMCW signal can be widely tuned from 11.41 to 50.05 GHz by simply adjusting injection parameters while the frequency sweep range of the FMCW signal can be controlled by varying the modulation index. Under proper operating parameters, the sweep range and rate of the FMCW signal are 18.42 GHz (13.73 GHz- 32.15 GHz) and 1.14 GHz/ns, respectively. Further, by introducing an optical feedback loop, the frequency comb contrast of the FMCW signal is drastically increased by 27.15 dB when the reciprocal of the feedback delay time matches with the modulation frequency exactly due to the locking effect of the external cavity optical modes.