Search

Abstract: We investigated the fluorescence characteristics of the bismuth doped silica fibers with and without Al co-dopant which are fabricated by means of modified chemical vapour deposition (MCVD) technique. It was found that the bismuth and germanium codoped silica fiber exhibited a strong broad infrared emission centring at 1450nm and covering 1300nm when excited by the laser diodes working at 808nm and 976nm respectively. It was also found that for the Al and bismuth codoped silica fiber, the red (centring around 750nm) and the infrared fluorescence (centring around 1100nm) may originate from different emission centers in the fiber. Furthermore, strong up-conversion luminescence was also observed in both Al codoped and non-Al codoped bismuth doped fibers when the fibers were excited by an acoustic-optic Q-switched Nd:YVO4 laser. It is thus concluded that the upper energy level absorption reported in the work of the bismuth doped silica fiber lasers may result from the fluorescence emission sites not responsible for the infrared emission. [Copyright &y& Elsevier]

Background: Extrauterine growth restriction (EUGR) represents a prevalent condition observed in preterm neonates, which poses potential adverse implications for both neonatal development and long-term health outcomes. The manifestation of EUGR has been intricately associated with perturbations in microbial and metabolic profiles. This study aimed to investigate the characteristics of the gut microbial network in early colonizers among preterm neonates with EUGR. Methods: Twenty-nine preterm infants participated in this study, comprising 14 subjects in the EUGR group and 15 in the normal growth (AGA) group. Meconium (D1) and fecal samples were collected at postnatal day 28 (D28) and 1 month after discharge (M1). Subsequently, total bacterial DNA was extracted and sequenced using the Illumina MiSeq system, targeting the V3-V4 hyper-variable regions of the 16S rRNA gene. Results: The outcomes of principal coordinates analysis (PCoA) and examination of the microbial network structure revealed distinctive developmental trajectories in the gut microbiome during the initial three months of life among preterm neonates with and without EUGR. Significant differences in microbial community were observed at the D1 (P = 0.039) and M1 phases (P = 0.036) between the EUGR and AGA groups, while a comparable microbial community was noted at the D28 phase (P = 0.414). Moreover, relative to the AGA group, the EUGR group exhibited significantly lower relative abundances of bacteria associated with secretion of short-chain fatty acids, including Lactobacillus (P = 0.041) and Parabacteroides (P = 0.033) at the D1 phase, Bifidobacterium at the D28 phase, and genera Dysgonomonas (P = 0.042), Dialister (P = 0.02), Dorea (P = 0.042), and Fusobacterium (P = 0.017) at the M1 phase. Conclusion: Overall, the present findings offer crucial important insights into the distinctive gut microbial signatures exhibited by earlier colonizers in preterm neonates with EUGR. Further mechanistic studies are needed to establish whether these differences are the cause or a consequence of EUGR. [ABSTRACT FROM AUTHOR]

Highlights: This review introduces the potential of 2D electronics for post-Moore era and discusses their current progress in digital circuits, analog circuits, heterogeneous integration, sensing circuits, artificial intelligence chips, and quantum chips in sequence. A comprehensive analysis of the current trends and challenges encountered in the development of 2D materials is summarized. An in-depth roadmap outlining the future development of 2D electronics is presented, and the most accessible and promising avenues for 2D electronics are suggested. Due to the constraints imposed by physical effects and performance degradation, silicon-based chip technology is facing certain limitations in sustaining the advancement of Moore's law. Two-dimensional (2D) materials have emerged as highly promising candidates for the post-Moore era, offering significant potential in domains such as integrated circuits and next-generation computing. Here, in this review, the progress of 2D semiconductors in process engineering and various electronic applications are summarized. A careful introduction of material synthesis, transistor engineering focused on device configuration, dielectric engineering, contact engineering, and material integration are given first. Then 2D transistors for certain electronic applications including digital and analog circuits, heterogeneous integration chips, and sensing circuits are discussed. Moreover, several promising applications (artificial intelligence chips and quantum chips) based on specific mechanism devices are introduced. Finally, the challenges for 2D materials encountered in achieving circuit-level or system-level applications are analyzed, and potential development pathways or roadmaps are further speculated and outlooked. [ABSTRACT FROM AUTHOR]

Highlights • A spherical DNAzyme-based two-photon nanoprobe has been developed for high sensitive and selective monitoring of miRNA in live cells. • DNAzyme has the significant signal amplification ability. • The SNA probe has the properties of resistance to enzymatic degradation, enhanced nucleic acid binding and excellent cellular uptake. • This two-photon SNA probe may serve as a new tool for getting insight into the functionality of miRNAs in a wide range of biological processes. Abstract Two-photon excitation (TPE) has excellent properties, such as lower tissue self-absorption and autofluorescence, reduced photodamage and photobleaching, and higher spatial resolution. Meanwhile, DNAzyme has significant signal amplification ability, and the gold nanoparticle (AuNP)-based spherical nucleic acid (SNA) has the properties of resistance to enzymatic degradation, enhanced nucleic acid binding and excellent cellular uptake. Taking advantage of their properties, in this work, we constructed a novel SNA-based TPE fluorescent DNAzyme probe for the selective and sensitive detection of target miRNA in living cells. Briefly, AuNPs were first functionalized with the substrate sequences hybridized to two split fragments of the 8–17 DNAzyme-contained sequence. Then, numerous two-photon absorption (TPA)-dye molecules of Ethyl-4-[3,6-Bis (1-methyl-4-vinylpyridium iodine)-9 H -carbazol-9-yl)] (EBMVC) were inserted into the substrate/split-DNAzyme duplexes on the surface of the AuNP to form the TPE SNA nanoprobe in the "off" fluorescence emission state. When the target miRNA is bound, the conformation of the split DNAzymes will change resulting in the activation of their catalytic ability, thus leading to cleavage of the substrate sequences and the release of the TPA-dye molecules-inserted DNAzyme motif from the surface of the AuNP. Concurrently, the released target miRNA would autonomously hybridize with another split DNAzyme motif and activate further cleavage reactions. This would induce the gradual dissociation of the TPA-dye molecules-inserted DNAzyme motifs from the surface of the AuNP through the repeated target miRNA hybridization-activated cleavage reaction and thereby trigger the cascade TPE fluorescence emission, ultimately achieving the detection of the miRNA through amplification of the fluorescence signals. The assay was successfully validated with clean buffer conditions as well as with cells. [ABSTRACT FROM AUTHOR]

In this paper, a flexible terahertz (THz) Metamaterial (MM) with high sensitivity is proposed for the detection of the pesticide imidacloprid. The MM sensor is composed of a polyimide (PI) substrate and a periodic aluminum (Al) split ring resonator array. The sensing performance of the MM is verified by both simulation and experiment. The simulation results show that the refractive index (RI) sensitivity of the proposed MM sensor is 220.7 GHz/RIU, and the figure of merit (FOM) of this MM is 1.52. Then, the sensing performance of the MM sensor is verified by using imidacloprid solutions with different concentrations. The experimental results show that the detection sensitivity of the MM sensor is 12.3 GHz/(mg/ml), and the limit of detection (LOD) is 0.0112 mg/ml. The THz MM sensor proposed in this paper is flexible, simple to make, cost-effective, highly sensitive and has a very broad application prospect in the concentration detection of pesticides such as imidacloprid. • The sensor has high refractive index sensitivity, concentration sensitivity and low detection limit. • The sensor is flexible and suitable for use in most cases. • The sensor material is cheap and easy to manufacture. • The shift of resonance peak under different structural parameters is analyzed. [ABSTRACT FROM AUTHOR]

Recovering the wavelengths from disordered speckle patterns has emerged as an exciting prospect as a wavelength measurement method due to its combination of high resolution and straightforward design. In previous studies, panel cameras were commonly utilized as the speckle image receiver. However, high cost (especially in a near-infrared range), bulky size, and low speed have limited its application in optical communications, metrology, and optical sensing. In this work, we effectively compressed speckle patterns into four intensities by using a quadrant detector (QD), bypassing the need for millions of pixels as in conventional cameras. Remarkably, wavelengths can still be recovered through only these four pixels. A new CNN based demodulation algorithm, shallow residual network (SRN), was proposed to recognize the wavelengths from the highly compressed speckle images. Finally, a wavelength precision of 4 fm (∼ 0.5 MHz) with an updating speed of ∼ 1 kHz was achieved in the demonstrations. In addition, the SRN shows a broad measurement range and good noise robustness. Compared with a camera-based system, the QD detection scheme associated with the CNN algorithm provides a compact, high-speed, and low-cost method to examine the speckle patterns, which opens new routes in many other fields. [ABSTRACT FROM AUTHOR]

China's BDS-3 global navigation satellite system has been built and is providing official open Positioning, Navigation, and Timing (PNT) service with full operational capability (FOC) since July 2020. The main new civil B1C and B2a ranging code signals are broadcasted on the two carriers with central frequencies of 1575.42 MHz and 1176.45 MHz, which were shared by other GNSSs. Compared with traditional signals, such as GPS L1 C/A and BDS B1I, the new civil signals have better modulation and wider bandwidth to be expected to achieve a better range performance. In order to evaluate code ranging accuracies directly, a zero-baseline experiment using a geodetic GNSS antenna and a four-channel intermediate frequency (IF) signal recorder was conducted. Two channels were used to receive the signals with a central frequency of 1575.42 MHz at a 62 MHz sampling rate, and the other two channels are for 1176.45 MHz. The raw IF data were post-processed using a software-defined receiver (SDR) to compute the code signal path differences between two channels with the same frequencies. Compared with the traditional hardware receiver, SDR has the characteristics of flexible use and good operability, but its running speed is slow. The root-mean-square (RMS) and bias values of the path differences from BDS B1C, BDS B2a, and GPS L5C were used to evaluate their accuracies. The results show that there is a weak negative correlation between the satellite elevation and the ranging accuracy when the satellite elevation ranges from 30° to 90°. The ranging accuracy of the B1C signal is lower than that of B2a, which may be caused by different code rates, bandwidth, and signal structure. The GPS L5C is used for precision analysis as a comparison. It shows that the code signal path differences accuracy of L5C is close to the B2a. [ABSTRACT FROM AUTHOR]

Urban resilience to natural disasters (e.g., flooding), in the context of climate change, has been becoming increasingly important for the sustainable development of cities. This paper presents a method to assess the urban resilience to flooding in terms of the recovery rate of different subdistricts in a city using all-weather synthetic aperture radar imagery (i.e., Sentinel-1A imagery). The factors that influence resilience, and their relative importance, are then determined through principal component analysis. Jakarta, a flood-prone city in Indonesia, is selected as a case study. The resilience of 42 subdistricts in Jakarta, with their gross domestic product data super-resolved using nighttime-light satellite images, was assessed. The association between resilience levels and influencing factors, such as topology, mixtures of religion, and points-of-interest density, were subsequently derived. Topographic factors, such as elevation (coefficient = 0.3784) and slope (coefficient = 0.1079), were found to have the strongest positive influence on flood recovery, whereas population density (coefficient = −0.1774) a negative effect. These findings provide evidence for policymakers to make more pertinent strategies to improve flood resilience, especially in subdistricts with lower resilience levels. [ABSTRACT FROM AUTHOR]

X‐ray radiation is a leading cause of cancer, and thus a device that offers effective and real‐time radiation monitoring is of significant interest. The configuration design, fiber drawing, and device construction are introduced for a multimaterial fiber detector system that allows real‐time and remote X‐ray monitoring. A fiber detector embedded with metal–semiconductor–insulator ladder‐like configuration is designed and successfully constructed on the basis of Plateau–Rayleigh instability. The multimaterial design affords the detector robust radiation‐harvesting ability, enabling the collection of up to ≈88.13% of total X‐ray energy. The unique ladder‐like configuration allows the efficient generation and collection of free charges. Moreover, the detector exhibits excellent mechanical flexibility and can be woven into a complex configuration and even wearable fabrics. Finally, the application of the micro‐detector in real‐time wireless X‐ray monitoring is demonstrated. This research not only presents a flexible radiation detection strategy for various ionizing radiation types, such as X‐ray, gamma ray, and neutrons radiation, but also has potential uses in remote radiation monitoring in case a conventional rigid device is inapplicable. [ABSTRACT FROM AUTHOR]

• We detect the fluctuations of the laser scan by a magneto-optic wavemeter. • We proposed a novel FBG demodulator contain a Faraday rotation wavemeter. • The FBG interrogation accuracy was raised to ±1 pm, better stability was achieved. Fiber Bragg grating (FBG) demodulators based on tunable lasers have been extensively applied in many fields. However, the tunable lasers can hardly avoid wavelength nonlinear tuning. Such problems and unexpected wavelength fluctuations may cause serious measurement errors. In this study, we propose a wavelength calibration scheme to solve this problem by incorporating a magneto-optic wavemeter into the interrogation system. We present experimental verification of real-time wavelength calibration of tunable lasers and measurement corrections. In the temperature measurement demonstrations, the experimental results show that the FBG interrogation accuracy was raised from ±3 pm to ±1 pm, and better long-term stability was achieved, corresponding to the temperature accuracy of ±0.1 °C. [ABSTRACT FROM AUTHOR]

• Optical fiber sensor demodulation by MEMS tunable filter. • Wavelength calibration by dual etalons with complimentary phase shift. • Demonstration of the proposed system in fiber Bragg grating and Fabry-Pérot sensors. An optical fiber sensor (OFS) demodulation system based on Micro-Electro-Mechanical System (MEMS) tunable filter (MTF) has been proposed and demonstrated in this study. By scanning the MTF, the acquired OFS curves were considered as the convolution of the tunable filter function and the real OFS spectrum. However, the wavelength setting error of the MTF significantly limited the measurement accuracy of the proposed demodulation system. To solve the problem, dual etalons with complementary phase shifts were adopted to calibrate the MTF in real time. For demonstration, a fiber Bragg grating and an open cavity Fabry-Pérot sensor were successfully demodulated by the MTF. Experimental results indicated that the measurement error of the MTF demodulator was improved from ±31 pm to ±3 pm, with the sensing resolution of 0.1 °C and 0.01 MPa, better than traditional grating-based spectrometers.. [ABSTRACT FROM AUTHOR]

A low-cost near-infrared spectrometer based on fiber beam scanning and linear variable filter (LVF) was proposed and demonstrated. The key elements of the spectrometer include a piezoelectric driven fiber scanner, an LVF monochromator, and a single point detector. The single fiber scanner provides a new way to continuously sweep the LVF. A PIN photodiode behind the LVF monochromator can acquire more spectral information than the traditional linear array detection. The performance of the spectrometer was verified with a narrow band tunable laser and a broadband light source. With the help of a deconvolution algorithm, the spectral resolution of the proposed spectrometer is up to 0.32% of the center wavelength (≈5 nm@1550 nm). [ABSTRACT FROM AUTHOR]

Hyperspectral image (HSI) contains both spatial pattern and spectral information, which has been widely used in food safety, remote sensing, and medical detection. However, the acquisition of HSIs is usually costly due to the complicated apparatus for the acquisition of optical spectrum. Recently, it has been reported that HSI can be reconstructed from single RGB image using convolution neural network (CNN) algorithms. Compared with the traditional hyperspectral cameras, the method based on CNN algorithms is simple, portable, and low cost. In this study, we focused on the influence of the RGB camera spectral sensitivity (CSS) on the HSI. A xenon lamp incorporated with a monochromator was used as the standard light source to calibrate the CSS. And the experimental results show that the CSS plays a significant role in the reconstruction accuracy of an HSI. In addition, we proposed a new HSI reconstruction network where the dimensional structure of the original hyperspectral datacube was modified by 3D matrix transpose to improve the reconstruction accuracy. [ABSTRACT FROM AUTHOR]

• The results show that the diffusion energy barrier of Na in Bco-C 16 is small, indicating an excellent mobility rate. • The volume changes little and the conductivity becomes better in the charging process. • It is sspeculated that Bco-C 16 could be a promising anode material for NIBs by the first-principle calculations. Sodium-ion batteries (NIBs) are considered to be reasonable alternatives for lithium-ion batteries (LIBs). Currently, searching high performance anodes is a key challenge for rechargeable NIBs. Using the first-principle method, we have investigated properties of body-centered orthorhombic carbon structure (bco-C 16) as anode materials for NIBs. 4 Na ions can be adsorbed stably in the structure at most as an electrode material of battery, and its maximum capacity is correspondingly 160.49 mAh/g. The diffusion energy barrier of Na in bco-C 16 is small as 9 meV, mirroring an excellent mobility rate. Together with the small volume change and better conductivity as Na ions inserted, we suggest that bco-C 16 has great potential to be an excellent all-carbon-based semimetal for NIBs anode material. [ABSTRACT FROM AUTHOR]