Down-conversion and frequency spectrum convolution of the broadband signal based on active mode-locking technology.

A multifunction processor for a broadband signal based on the active mode-locking optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The central frequency down-conversion and frequency spectrum convolution of the target broadband signal (TBS) are realized by just tuning the wavelength of the optical carrier or by the time domain product, respectively. To achieve the central frequency down-conversion of the TBS, an optical tunable delay line (OTDL) is adopted to match the delay time of the OEO loop with the repetition period of the TBS. Then the spectrum convolution of the TBS is produced by just injecting a lower frequency signal consistent with the free spectral range (FSR) of the OEO loop. Moreover, the frequency convolution repetition is also greatly increased by harmonic mode-locking injection. The equivalent bandwidth of the TBS is enlarged by ∼50 times, benefiting from the frequency convolution. The central frequency conversion flexibility and the bandwidth compatibility are also discussed in detail. This work provides a multifunction processor system and may have potential usage in multifunctional integrated radar systems.

Highly improved side mode suppression ratio and a low phase noise optoelectronic oscillator.

By adopting self-injection locking (SIL) technology in an external injection locking (EIL) optoelectronic oscillator (OEO), a highly improved side mode suppression ratio (SMSR) and low phase noise microwave signal generator is designed. The EIL ranging is closely related to the frequency spacing ranging of the free-running OEO, which is the reverse of the oscillation loop length, and limits the phase noise performance. Here SIL technology is introduced to significantly increase the Q-factor of the OEO without degrading the SMSR by setting the longer loop without oscillation. Both the simulation and experimental results are carried out to confirm the conclusion. Additionally, an SMSR up to 86 dB and phase noises as low as -88.80dBc/Hz@100Hz and -122.83dBc/Hz@10kHz, respectively, are demonstrated. Furthermore, the frequency overlapping Allan deviation of the proposed OEO scheme is also enhanced by 103 times, which benefits from the external injection technology compared with the free-running OEO. In addition, the SMSR and phase noise modification dependence on the fiber length, the RF source quality and external injection power, as well as the frequency tunability, are detailed and discussed to reveal the compatibility combination mechanism of the EIL and the SIL.

Active mode lock optoelectronic oscillator based on the simulated Brillouin scattering effect.

An active mode-locked optoelectronic oscillator (AML-OEO) based on the simulated Brillouin scattering (SBS) effect without an electrical filter is demonstrated here. By using phase modulation and SBS-based selective sideband amplification, the central frequency of the proposed SBS-AML-OEO is easily adjusted by simply changing the pump laser frequency instead of the filters. A microwave frequency comb signal with an adjustable central frequency and fixed bandwidth are generated by injecting a mode-locking external RF synchronizing with the free spectral ranging FSR. In addition, the harmonic SBS-AML-OEO is also achieved by harmonic signal injection. The proposed method reveals a simple solution to tune the central frequency and has the potential to be integrated on a chip since there is no structure changing in the scheme.

Value of sufficient clean intermittent catheterization in urinary tract infection and upper urinary tract protection in children with neurogenic bladder.

INTRODUCTION: Clean intermittent catheterization (CIC) is a mainstay in the management of neurogenic bladder. OBJECTIVE: To assess the effect of CIC on urinary tract infection and upper renal tract function in pediatric patients with neurogenic bladder, and the influence of duration of CIC on these variables. STUDY DESIGN: A retrospective study was performed in 67 pediatric patients with neurogenic bladder who started CIC between 2014 and 2019 at our institution. The febrile urinary tract infection (fUTI) rate, renal pelvis diameter (measured by antero-posterior renal pelvis diameter, APPD), bladder wall thickness (BWT) on ultrasound, and creatinine level at 6 months and 12 months of CIC were compared with baseline in all patients. The grade of vesicoureteral reflux (VUR) at 12 months of CIC were also compared with baseline. RESULTS: There were no significant differences compared with baseline after 6 months of CIC in the rate of fUTI, APPD, and BWT (p > 0.05); however, all of these parameters significantly improved after 12 months of CIC (p < 0.05). The VUR grade was significantly reduced after 12 months of CIC(p = 0.03). There was no significant change in serum creatinine level with any duration of CIC (both p > 0.05). DISCUSSION: Continuing CIC for more than 6 months had a beneficial influence on protecting the upper urinary tract. Complications of CIC, such as recurrent fUTI and lower urinary tract trauma, are more likely to occur in the early stage of CIC due to poor technique by the caregivers and poor patient compliance underscoring the importance of caregiver education. Study limitations include the retrospective nature and small sample size. CONCLUSION: CIC for less than 6 months may have limited influence on renal protection; however, a longer duration of CIC (12 months) resulted in significant improvement in outcomes. This study demonstrates the importance of proper caregiver education to establish standardized CIC techniques and to improve CIC quality.

Microwave photonic radar system with ultra-flexible frequency-domain tunability.

Both effective detection demand against diversified development of flight targets and remote sensing providing identifiable and fine target information all call for microwave radar system with flexible and ultra-wideband frequency-domain ability to provide more high-resolution and multi-source information. A microwave photonic radar system with theoretically full-band and ultra-wideband working ability is presented and experimentally demonstrated. An optical frequency operation module is employed in the transmitter to break the frequency-domain limitation on the emitted radar signal, while two types of optical mixing structures are switched to provide the ability to receive target echoes at any frequency band. In the experiments, high-SNR optical frequency operation and subsequent waveform generation at each normal radar band, that is from HF to Ka, are carried out. Good linearity and coherence of the generated waveforms are also demonstrated. Then, multi-band system-level detection experiments are completed to show the full-band working ability. Centimeter-scale or even sub-centimeter-scale resolution are realized at different bands, which identifies the proposed system can handle target detection with flexible performance and support acquiring rich target information at different frequency bands in future.

Posterior Urethral Valves with Lower Urinary Tract Symptoms: Perspective on Urodynamics.

BACKGROUND: Lower urinary tract symptoms (LUTs) are common in young boys with posterior urethral valves (PUVs). It is crucial to investigate the characteristics of PUV patients with and without LUTs after valve ablation. METHODS: Between January 2017 and December 2019, PUV patients visited Children's Hospital, Fudan University for following up were enrolled. Medical records and information from the patients' urodynamic studies (UDS) were reviewed. RESULTS: A total of 54 enrolled PUV patients were divided into symptomatic PUV group (28 cases) and non-symptomatic PUV group (26 cases) according to daytime incontinence or not, and 21 OAB cases without structural abnormalities were set as UDS control group. The non-symptomatic PUV patients had lager filling volume (135 ± 46% of EBC) than the symptomatic PUV patients and OAB patients (106.1 ± 44.4% of EBC, p = 0.0255 and 88.1 ± 39.6% of EBC, p = 0.0007, respectively). The detrusor pressure at 1/4 and 3/4 of full filling was higher in PUV groups than the control group, but no significant difference was found between the PUV groups. PUV patients with LUTs had a higher rate (19/28, 67.9%) of impaired bladder compliance than non-symptomatic PUV patients (11/26, 42.3%, p = 0.0489). The PUV patients with LUTs had a trend of worse kidney functions in lower GFR, higher serum creatinine and lower estimated GFR. CONCLUSION: PUV patients have higher detrusor pressure regardless of the presence or absence of LUT symptoms. Bladder function assessments are needed in boys with PUV, even without incontinence symptoms after valve ablation.

Tactile perception of randomly rough surfaces.

Most everyday surfaces are randomly rough and self-similar on sufficiently small scales. We investigated the tactile perception of randomly rough surfaces using 3D-printed samples, where the topographic structure and the statistical properties of scale-dependent roughness were varied independently. We found that the tactile perception of similarity between surfaces was dominated by the statistical micro-scale roughness rather than by their topographic resemblance. Participants were able to notice differences in the Hurst roughness exponent of 0.2, or a difference in surface curvature of 0.8 [Formula: see text] for surfaces with curvatures between 1 and 3 [Formula: see text]. In contrast, visual perception of similarity between color-coded images of the surface height was dominated by their topographic resemblance. We conclude that vibration cues from roughness at the length scale of the finger ridge distance distract the participants from including the topography into the judgement of similarity. The interaction between surface asperities and fingertip skin led to higher friction for higher micro-scale roughness. Individual friction data allowed us to construct a psychometric curve which relates similarity decisions to differences in friction. Participants noticed differences in the friction coefficient as small as 0.035 for samples with friction coefficients between 0.34 and 0.45.

Ka-band microwave photonic ultra-wideband imaging radar for capturing quantitative target information.

Extracting precise target characteristics from microwave image is needed and calls for high-resolution microwave imaging radar systems. In this paper, a Ka-band ultra-wideband microwave photonic (MWP) imaging radar is developed and experimentally demonstrated. In the transmitter, continuous ultra-wideband linear frequency modulation (LFM) wave is generated based on optical frequency sextupling technique. In the receiver, a combination of optical frequency mixer with fiber delay lines and electric analog-to-digital converter (ADC) is capable of receiving target echoes and imaging targets with different distances. The maximum instantaneous bandwidth of the transmitted waveform is measured to be 10.02 GHz and corresponding range resolution is calibrated to be 1.68 cm. Out-field tests with demonstrator working at synthetic aperture radar (SAR) or inverse synthetic aperture radar (ISAR) mode are carried out. Different targets such as an unmanned aerial vehicle (UAV), airliner and Leifeng pagoda are imaged. Based on corresponding high-resolution microwave images, quantitative information of the targets can be identified, which shows the great potential of the radar demonstrator for various remote sensing applications.

Label-free brainwide visualization of senile plaque using cryo-micro-optical sectioning tomography.

Optical visualization of pathological changes in Alzheimer's disease (AD) can facilitate exploration of disease mechanisms and treatments. However, existing optical imaging methods have limitations on mapping pathological evolution in the whole mouse brain. Previous research indicated endogenous fluorescence contrast of senile plaques. Therefore, we develop cryo-micro-optical sectioning tomography (cryo-MOST) to capture intrinsic fluorescence distribution of senile plaques at a micrometer-level resolution in the whole brain. Validation using immunofluorescence demonstrates the capacity of cryo-MOST to visualize and distinguish senile plaques with competent sensitivity and spatial resolution. Compared with imaging in room temperature, cryo-MOST provides better signal intensity and signal-to-noise ratio. Using cryo-MOST, we obtained whole-brain coronal distribution of senile plaques in a transgenic mouse without exogenous dye. Capable of label-free brainwide visualization of Alzheimer's pathology, cryo-MOST may be potentially useful for understanding neurodegenerative disease mechanisms and evaluating drug efficacy.

Atomistic dynamics of sulfur-deficient high-symmetry grain boundaries in molybdenum disulfide.

As a common type of structural defect, grain boundaries (GBs) play an important role in tailoring the physical and chemical properties of bulk crystals and their two-dimensional (2D) counterparts such as graphene and molybdenum disulfide (MoS2). In this study, we explore the atomic structures and dynamics of three kinds of high-symmetry GBs (α, ß and γ) in monolayer MoS2. Atomic-resolution transmission electron microscopy (TEM) is used to characterize their formation and evolutionary dynamics, and atomistic simulation based analysis explains the size distribution of α-type GBs observed under TEM and the inter-GB interaction, revealing the stabilization mechanism of GBs by pre-existing sulfur vacancies. The results elucidate the correlation between the observed GB dynamics and the migration of sulfur atoms across GBs via a vacancy-mediated mechanism, offering a new perspective for GB engineering in monolayer MoS2, which may be generalized to other transition metal dichalcogenides.

Optimization of sample cooling temperature for redox cryo-imaging.

Cryo-imaging techniques have been widely used to measure the metabolic state of tissues by capturing reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) autofluorescence. However, NADH and FAD fluorescence is sensitive to changes in temperature, which may result in unreliable redox ratio calculations. Here, the relationship between the measured redox ratio and sample surface temperature was analyzed using a standard phantom solution and biological tissues. The results indicated that a temperature < - 100°C was a suitable cryo-imaging temperature window in which redox ratio measuring was immune to temperature fluctuations. These results may serve as a reference for designing and optimizing redox cryo-imaging experiments for quantitatively mapping the metabolic state of biological samples.

Quality evaluation method for rat brain cryofixation on the basis of NADH fluorescence.

The goal of biological samples' cryofixation is to trap a metabolic state as it exists in vivo by rapidly stopping internal reactions. However, obtaining perfect quality of cryofixation for large and high hypermetabolism organ/tissue (such as brain, heart) remains a challenge. The aim of this study was to develop and display a comprehensive and direct method to evaluate cryofixation's process and quality. Here, we adopt a delicate combination of homemade cryo-imaging system with a rat cardiac arrest model that can control cryofixation time optionally. we successfully evaluate the cryofixation time-related nicotinamide adenine dinucleotide (NADH) fluorescence pattern of several coronal sections in rat's brain that suffered from directional funnel cryofixation procedure. Through quantitative analysis of the distribution map of NADH fluorescence, we could obtain a relationship between cryofixation time and well cryofixation volume and then could deduce the cryofixation rates and quality at different time points. Our results also demonstrated that dissection of the temporal muscle of rat could significantly optimize the classical direct funnel cryofixation protocol.

Fluorescence ghost imaging with pseudothermal light.

We extend classical light ghost imaging to the area of fluorescence imaging and propose a new fluorescence imaging method. For the first time, we demonstrate both theoretically and experimentally that fluorescence ghost imaging can be realized with pseudothermal light. Important factors influencing the visibility and resolution of the images are discussed to improve the quality of the fluorescence ghost imaging. We hope that this work may pave the road for ghost imaging to biomedical applications.