Dual-mode transfer response based on electrochemical and fluorescence signals for the detection of amyloid-beta oligomers (AßO).

An aptamer sensor has been developed utilizing a dual-mode and stimuli-responsive strategy for quantitative detection of AßO (amyloid-beta oligomers) through simultaneous electrochemical and fluorescence detection. To achieve this, we employed UIO-66-NH2 as a carrier container to load MB (Methylene Blue), and Fe3O4 MNPs (iron oxide magnetic nanoparticles) with aptamer (ssDNA-Fe3O4 MNPs) fixed on their surface for biological gating. The ssDNA-Fe3O4 MNPs were immobilized onto the surface of UIO-66-NH2 through hydrogen bonding between the aptamer and the -NH2 group on the surface of UIO-66-NH2, thereby encapsulating MB and forming ssDNA-Fe3O4@MB@UIO-66-NH2. During the detection of AßO, the aptamer selectively reacted with AßO to form the AßO-ssDNA-Fe3O4 complex, leading to its detachment from the surface of UIO-66-NH2. This detachment facilitated the release of MB, enabling its electrochemical detection. Simultaneously, the AßO-ssDNA-Fe3O4 complex was efficiently collected and separated using a magnet after leaving the container's surface. Furthermore, the addition of NaOH facilitated the disconnection of biotin modifications at the 3' end of the aptamer from the avidin modifications on the Fe3O4 MNPs. Consequently, the aptamer detached from the surface of Fe3O4 MNPs, resulting in the restoration of fluorescence intensity of FAM (fluorescein-5'-carboxamidite) modified at its 5' end for fluorescence detection. The dual-mode sensor exhibited significantly enhanced differential pulse voltammetry signals and fluorescence intensity compared to those in the absence of AßO. The sensor demonstrated a wide detection range of 10 fM to 10 µM, with a detection limit of 3.4 fM. It displayed excellent performance in detecting actual samples and holds promising prospects for early diagnosis of Alzheimer's disease.

High-speed serial deep learning through temporal optical neurons.

Deep learning is able to functionally mimic the human brain and thus, it has attracted considerable recent interest. Optics-assisted deep learning is a promising approach to improve forward-propagation speed and reduce the power consumption of electronic-assisted techniques. However, present methods are based on a parallel processing approach that is inherently ineffective in dealing with the serial data signals at the core of information and communication technologies. Here, we propose and demonstrate a sequential optical deep learning concept that is specifically designed to directly process high-speed serial data. By utilizing ultra-short optical pulses as the information carriers, the neurons are distributed at different time slots in a serial pattern, and interconnected to each other through group delay dispersion. A 4-layer serial optical neural network (SONN) was constructed and trained for classification of both analog and digital signals with simulated accuracy rates of over 79.2% with proper individuality variance rates. Furthermore, we performed a proof-of-concept experiment of a pseudo-3-layer SONN to successfully recognize the ASCII codes of English letters at a data rate of 12 gigabits per second. This concept represents a novel one-dimensional realization of artificial neural networks, enabling a direct application of optical deep learning methods to the analysis and processing of serial data signals, while offering a new overall perspective for temporal signal processing.

Anaerobically fermented spent mushroom substrates improve nitrogen removal and lead (II) adsorption.

In this study, spent mushroom substrates (SMSs) were fermented anaerobically at room temperature to gain liquid SMSs (LSMSs) that were used to remove nitrogen from the piggery wastewater with a low C/N ratio in a sequencing batch reactor (SBR) and solid SMSs (SSMSs) that were utilized to adsorb Pb2+ from Pb2+-containing wastewater in a fixed-bed reactor (FBR). After LSMSs supplement, the removal efficiency of both total nitrogen (TN) and NH+4-N increased from around 50% to 60-80%. High-throughput sequencing results presented an obvious change in microbial diversity, and some functional microorganisms like Zoogloea and Hydrogenophaga predominated to promote nitrogen removal. Pb2+ did not emerge from the effluent until 240 min with the corresponding concentration being less than 3 mg/L when using 30-day SSMSs as adsorbents, and it was demonstrated to be appropriate to use the Thomas model to predict Pb2+ sorption on SSMSs. Although various functional groups played a role in binding ions, the carboxyl group was proved to contribute most to Pb2+ adsorption. These results certified that the anaerobically fermented SMSs are decidedly suitable for wastewater treatment.

Optical phase matching of high-order azimuthal WGM in a water droplet resonator.

We observe the optical phase matching between a fiber taper and a high-order azimuthal whispering gallery mode (WGM) in a water droplet for the first time. The eccentricity of the droplet separates the wavelength of azimuthal modes. We evaluate the optical phase matching between the fiber taper mode and different azimuthal modes. In the experiments, the phase matching of a high-order azimuthal WGM (l-|m|=6) is realized around 1550 nm. The lifted azimuthal modes make high-efficient coupling easier for a probing light with narrow spectral range. They also have potential applications in detecting the shape fluctuation and eccentricity of water droplets.

Large-capacity and low-loss integrated optical buffer.

Temporarily storing light occupies a pivotal position in all-optical packet switching network and microwave photonics. An integrated optical buffer with large capacity and low loss is demonstrated on a silica wafer. The optical buffer consists of four silica waveguide delay lines connected by five thermo-optic switches. With different switch combinations applied, related delay lines are selected to realize a different storage time in the buffer, and a storage time up to 100 ns with a 10-ns step size is implemented. By optimizing the fabrication process and introducing the offsets between straight and bending waveguides, the propagation loss as low as ~1.08 dB/m is achieved. This large-capacity and low-loss buffer enables broad applications in optical communications and microwave photonics.

Time-stretch probing of ultra-fast soliton dynamics related to Q-switched instabilities in mode-locked fiber laser.

Ultra-fast soliton dynamics is one of the most attractive phenomena in the mode-locked fiber laser. However, the formation and breakup of solitons are difficult to observe, due to the transient nature of the process. Using the time-stretch technique, we are able to trace the real-time evolution of the soliton bound state formation and mode-locking build-up. Q-switched instabilities exist in both booting processes. Moreover, we find that the evolving patterns of soliton bound states are highly dependent on their initial conditions. Here, two types of soliton pairs are observed in the cavity and their typical forming dynamics are recorded and analyzed. Our findings uncover a diverse set of soliton dynamics in a mode-locked fiber laser and thus promote our understandings about complex dynamics in nonlinear optical systems. These results also provide a valuable reference for further theoretical studies.

Time-bandwidth compression of microwave signals.

We report and demonstrate a reconfigurable photonic anamorphic stretch transform to realize time-bandwidth product (TBP) compression for microwave signals. A time-spectrum convolution system is employed to provide an ultra-high nonlinear dispersion up to several nanoseconds per gigahertz, which is required for processing nanosecond-long microwave signals. The group delay of the system can be engineered easily by programming a WaveShaper. Based on the proposed scheme, the TBP of a double pulse microwave signal is compressed by 1.9 times. Our proposal can provide a more efficient way to sample, digitize and store high-speed microwave signals, opening up entirely new perspectives for generation of many critical microwave signal processing modules.

Photonic true time delay beamforming technique with ultra-fast beam scanning.

A photonic-based true time delay (TTD) phased array antenna (PAA) with ultra-fast angle scan is proposed and experimentally demonstrated. A tunable TTD is realized using a wavelength-swept laser and an array of dispersive elements. The key novelty of our work is the ultra-fast angle scan using an ultra-fast wavelength-swept laser source, which is constructed by a gated multi-wavelength laser (MWL) and a dispersion compensation fiber (DCF). In our experiments, a wavelength-sweep time between two adjacent wavelengths is only several nanoseconds for wavelength spacing of 2.4, and 3.2 nm. We successfully realized an ultra-fast angle scan from 0 to 43° with a step of 8.8° in 12.48 ns.

Femtosecond pulse shaping using wavelength-selective directional couplers: proposal and simulation.

The femtosecond pulse-shaping capabilities of wavelength-selective directional couplers are investigated. Numerical results show that, depending on the coupling length and coupling coefficient, one can achieve very different temporal shapes at the output of the directional couplers. For instance, temporal re-shaping of Gaussian-like pulses into Hermite-Gaussian pulses, parabolic pulses, square temporal waveforms and sequences of equalized multiple pulses with time widths down to the femtosecond range can be achieved using readily feasible fiber/waveguide designs. The detrimental influence of the second-order variation of the detuning factor in these pulse shapers is also numerically investigated.

Experimental demonstration of a multi-target detection technique using an X-band optically steered phased array radar.

An X-band optically-steered phased array radar is developed to demonstrate high resolution multi-target detection. The beam forming is implemented based on wavelength-swept true time delay (TTD) technique. The beam forming system has a wide direction tuning range of ± 54 degree, low magnitude ripple of ± 0.5 dB and small delay error of 0.13 ps/nm. To further verify performance of the proposed optically-steered phased array radar, three experiments are then carried out to implement the single and multiple target detection. A linearly chirped X-band microwave signal is used as radar signal which is finally compressed at the receiver to improve the detection accuracy. The ranging resolution for multi-target detection is up to 2 cm within the measuring distance over 4 m and the azimuth angle error is less than 4 degree.

Broadband microwave photonic phase shifter based on a feedback-coupled microring resonator with small radio frequency power variations.

An on-chip microwave photonic phase shifter based on an electrically tunable feedback-coupled microring resonator (FCMR) is proposed and experimentally demonstrated. By properly adjusting the voltage applied on the FCMR, the transmission spectrum with different optical extinction ratios is realized while the phase shift range remains almost unchanged. This proposal solves the conflict between the large range of phase shift and small radio frequency (RF) power variation in the ring-resonator-based microwave photonics phase shifter. Finally, a microwave photonic phase shifter with phase tuning of over 172 deg from 20 to 30 GHz is obtained, and the RF power variation can be compressed less than 5 dB under a certain status tuned by the bias voltage.

Nitrite removal by Acinetobacter sp.TX: a candidate of curbing N2O emission.

The nitrite removal pathway in Acinetobacter sp. TX5 was explored through the key gene identification and the corresponding enzyme purification, after which the capability to reduce nitrite by immobilized beads was investigated in a fixed-bed reactor. Results revealed that a nosZ gene encoding nitrous oxide reductase (N2OR) exists in TX5 cells, and a N2OR responsible for the reduction of N2O to N2 was purified successfully with a molecular weight of 70.05 kDa, a purification fold of 16.30 and a recovery rate of 5.17%. For TX5 immobilization, the optimal values of polyvinyl alcohol (PVA), spent mushroom substrate (SMS) and Aci (TX5) obtained by response surface methodology (RSM) were 6.32%, 2.92% and 4.57%, respectively. In a fixed-bed reactor packed with immobilized TX5, the removal efficiency (RE) achieved 90% (at 50 h) for NO2--N and 85% (at 96 h) for total nitrogen (TN). On the basis of these results, a nitrite removal pathway in TX5 was proposed. Overall, Acinetobacter sp. TX5 might be a promising candidate for nitrite removal with an ability to suppress N2O accumulation.

Identification of potential diagnostic biomarkers for Parkinson's disease.

The identification of biomarkers for early diagnosis of Parkinson's disease (PD) prior to the onset of symptoms may improve the effectiveness of therapy. To identify potential biomarkers, we downloaded microarray datasets of PD from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between PD and normal control (NC) groups were obtained, and the feature selection procedure and classification model were used to identify optimal diagnostic gene biomarkers for PD. A total of 1229 genes (640 up-regulated and 589 down-regulated) were obtained for PD, and nine DEGs (PTGDS, GPX3, SLC25A20, CACNA1D, LRRN3, POLR1D, ARHGAP26, TNFSF14 and VPS11) were selected as optimal PD biomarkers with great diagnostic value. These nine DEGs were significantly enriched in regulation of circadian sleep/wake cycle, sleep and gonadotropin-releasing hormone signaling pathway. Finally, we examined the expression of GPX3, SLC25A20, LRRN3 and POLR1D in blood samples of patients with PD by qRT-PCR. GPX3, LRRN3 and POLR1D exhibited the same expression pattern as in our analysis. In conclusion, this study identified nine DEGs that may serve as potential biomarkers of PD.

Piggery wastewater treatment by Acinetobacter sp. TX5 immobilized with spent mushroom substrate in a fixed-bed reactor.

Acinetobacter sp. TX5 immobilized with spent Hypsizygus marmoreus substrate (SHMS) was used to treat the raw piggery wastewater (RPW). In batch experiments, NH4+-N in the diluted RPW decreased from initial 34.95 mg/L to 3.83 mg/L at 8 h with the removal efficiency (RE) being 89%, and the beads immobilized with SHMS were comparable to those immobilized with activated carbon. In continuous experiments, the RE ranged from 74% to 95% for NH4+-N, from 73% to 93% for TN and from 54% to 82% for COD when the RPW was treated in a fixed-bed reactor packed with SHMS-immobilized TX5. The isotope analysis and enzyme purification indicated simultaneous nitrification and denitrification existing in TX5. This is the first time that spent mushroom substrates have been used to immobilize Acinetobacter species to treat the real RPW and a denitrifying nitrite reductase (dNiR) has been purified to make the nitrogen removal pathway in this species clearer.

Reconfigurable single-shot incoherent optical signal processing system for chirped microwave signal compression.

We propose and demonstrate a reconfigurable and single-shot incoherent optical signal processing system for chirped microwave signal compression, using a programmable optical filter and a multi-wavelength laser (MWL). The system is implemented by temporally modulating a specially shaped MWL followed by a suitable linear dispersive medium. A microwave dispersion value up to 1.33ns/GHz over several GHz bandwidth is achieved based on this approach. Here we demonstrate a single-shot compression for different linearly chirped microwave signals over several GHz bandwidth. In addition, the robustness of the proposed system when input RF signals are largely distorted is also discussed.

Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier.

All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.