Advanced fabrication of polymer waveguide interferometric sensor utilizing interconnected holey fibers.

A universally applicable approach is proposed for the fabrication of fiber-optic polymer sensors. The hollow-core fibers (HCFs) with inner diameters of 30 µm, 50 µm, and 75 µm are spliced coaxially with dual-hole fiber (DHF) or photonic crystal fiber (PCF). Owing to the sized-matched air holes within HCF and DHF/PCF, an interconnected in-fiber microchannel is constructed, which facilitates rapid and complete filling of the HCF's central hole with liquid glue. After the ultraviolet-induced polymerization, a polymer Fabry-Perot interferometer is achieved by cutting the HCF end with a desired cavity length. Besides, the interference visibility is significantly enhanced by adding a refractive-index-modulated polymer cap onto the cutting surface. Experimental results demonstrate the optimized interference spectra and the interconnection of the matched air-hole fibers. The polymer sensor exhibits a signal-to-noise ratio of 56.8 dB for detecting pulsed ultrasonic waves, which is more than twice that of a partially polymer-filled sensor. Due to the hermetically-sealed structure, the sensor probe presents constrained performance with a temperature sensitivity of 230.2 pm/°C and a humidity sensitivity of 93.7 pm/%RH, which can be further improved by releasing the polymer waveguide from fiber cladding. Based on interconnected holey fibers, the proposed approach has a uniform size-controlled polymer waveguide dimension with increased spectrum visibility, rendering it suitable for a diverse range of microstructure-matched optical fibers.

A comprehensive stem cell laboratory module with blended learning for medical students at Tongji University.

The laboratory practice "Primary culture and directional differentiation of rat bone marrow mesenchymal stem cells (BMSCs)" is part of a required course for sophomore medical students at Tongji university, which has been conducted since 2012. Blended learning has been widely applied in medical courses. Based on a student-centered teaching philosophy, we reconstructed a comprehensive stem cell laboratory module with blended learning in 2021, aiming to facilitate students in enhancing their understanding of the multi-lineage differentiation potential of stem cells and improve their experimental skills, self-directed learning ability, and innovative thinking. First, we constructed in-depth online study resources, including videos demonstrating laboratory procedures, a PowerPoint slide deck, and published literature on student self-learning before class. In class, students performed a primary culture of BMSCs, freely chose among adipogenic, osteogenic, or chondrogenic differentiation, and used cytochemical or immunofluorescence staining for identification. After class, the extracurricular part involved performing quantitative polymerase chain reaction to examine the expression of multi-lineage differentiation marker genes, which was designed as an elective. After 2 years of practice, positive feedback was obtained from both students and faculty members who achieved, the learning goal as expected. The reconstructed stem cell laboratory module provides comprehensive practice opportunities for students. Students have a better understanding of BMSC at the molecular, cellular, and functional levels and have improved their experimental skills, which forms a basis for scientific research for medical students. Introducing blended learning into other medical laboratory practices thus seems valuable.

Fiber-end suspended polymer micro-rod inscribed with Bragg grating for highly sensitive ultrasonic detection.

A suspended polymer rod grating is fabricated on a fiber end for highly sensitive ultrasonic detection. Initially, the uniform polymer waveguide is prepared via the interconnection of holey fibers and the photopolymerization of an ultraviolet glue. A femtosecond laser point-by-point technique is then employed to form periodic grating structures inside the customized waveguide. A final uncovered micro-rod is achieved based on different corrosion resistances of the polymer waveguide and the fiber cladding. The polymer rod presents uniform morphology and controllable size with the support of the constructed air-hole microchannel. The self-alignment and the self-adhesion between the polymer waveguide and the fiber core contribute to the stable efficient optical coupling at the fiber-to-polymer joint. When applied to ultrasonic waves, the decreased size and low Young's modulus of the suspended rod provide benefits for the interaction between the polymer grating and the ultrasound strain. This sensor exhibits a noise equivalent pressure of 33 Pa and -10 d B bandwidth of 7.6 MHz. After packing with a waterproof adhesive, the polymer rod shows sufficient robustness for long-term operation. This Letter proposes a new, to the best of our knowledge, strategy for the fabrication of advanced polymer probes in multifunctional sensing.

Advanced suspended-core fiber sensor for seismic physical modeling.

A micro ultrasonic sensor based on an advanced suspended-core fiber is proposed and employed for in-lab seismic physical modeling. A free suspended core is obtained by acid corrosion and two cascaded uniform fiber Bragg gratings (FBGs) are imprinted in the suspended-core fiber. The sensor response and stability are largely improved due to the using of dual-FBG reflectors instead of weak-reflection fiber mirrors for constructing an in-fiber interferometer. The characteristics of reflection spectra and ultrasonic response of the sensor are analyzed and demonstrated experimentally. Comparative measurements are also carried out to prove the sensor superiority over the conventional weak-reflection one. Moreover, the sensor is used for seismic physical modeling to show its ability of practicable usage. Both the crosswell seismic and surface seismic in seismic exploration are modeled respectively based on reservoir and fault models. Various reservoir velocities are measured and each is consistent with the reported results. The fault features are also well reconstructed in the form of a cross-section model image. The improved sensor approach greatly promotes the application of the suspended-core fiber for weak acoustic detection in seismic physical modeling.

Immune Profiling of Parkinson's Disease Revealed Its Association With a Subset of Infiltrating Cells and Signature Genes.

Parkinson's disease (PD) is an age-related and second most common neurodegenerative disorder. In recent years, increasing evidence revealed that peripheral immune cells might be able to infiltrate into brain tissues, which could arouse neuroinflammation and aggravate neurodegeneration. This study aimed to illuminate the landscape of peripheral immune cells and signature genes associated with immune infiltration in PD. Several transcriptomic datasets of substantia nigra (SN) from the Gene Expression Omnibus (GEO) database were separately collected as training cohort, testing cohort, and external validation cohort. The immunoscore of each sample calculated by single-sample gene set enrichment analysis was used to reflect the peripheral immune cell infiltration and to identify the differential immune cell types between PD and healthy participants. According to receiver operating characteristic (ROC) curve analysis, the immunoscore achieved an overall accuracy of the area under the curve (AUC) = 0.883 in the testing cohort, respectively. The immunoscore displayed good performance in the external validation cohort with an AUC of 0.745. The correlation analysis and logistic regression analysis were used to analyze the correlation between immune cells and PD, and mast cell was identified most associated with the occurrence of PD. Additionally, increased mast cells were also observed in our in vivo PD model. Weighted gene co-expression network analysis (WGCNA) was used to selected module genes related to a mast cell. The least absolute shrinkage and selection operator (LASSO) analysis and random-forest analysis were used to analyze module genes, and two hub genes RBM3 and AGTR1 were identified as associated with mast cells in the training cohort. The expression levels of RBM3 and AGTR1 in these cohorts and PD models revealed that these hub genes were significantly downregulated in PD. Moreover, the expression trend of the aforementioned two genes differed in mast cells and dopaminergic (DA) neurons. In conclusion, this study not only exhibited a landscape of immune infiltrating patterns in PD but also identified mast cells and two hub genes associated with the occurrence of PD, which provided potential therapeutic targets for PD patients (PDs).

[Research advance in circular RNAs].

Circular RNAs (circRNAs) are a class of endogenous, covalently closed, single-stranded RNA without 3'-poly(A) and 5'-cap structures. CircRNAs are characterized by universality, diversity, stability and conservation, and have been found to regulate mammalian transcription and be translated into proteins. In this review, we summarized the biogenesis, classification, expression, distribution, biological functions and regulation of circRNAs. In addition, we discussed the association of circRNAs with diseases and the methods for identification and characterization of circRNAs. Finally, we speculated the application prospect and research direction of circRNAs.

Long noncoding RNA CCDC144NL-AS1 knockdown induces naïve-like state conversion of human pluripotent stem cells.

BACKGROUND: Human naïve pluripotency state cells can be derived from direct isolation of inner cell mass or primed-to-naïve resetting of human embryonic stem cells (hESCs) through different combinations of transcription factors, small molecular inhibitors, and growth factors. Long noncoding RNAs (lncRNAs) have been identified to be crucial in diverse biological processes, including pluripotency regulatory circuit of mouse pluripotent stem cells (PSCs), but few are involved in human PSCs' regulation of pluripotency and naïve pluripotency derivation. This study initially planned to discover more lncRNAs possibly playing significant roles in the regulation of human PSCs' pluripotency, but accidently identified a lncRNA whose knockdown in human PSCs induced naïve-like pluripotency conversion. METHODS: Candidate lncRNAs tightly correlated with human pluripotency were screened from 55 RNA-seq data containing human ESC, human induced pluripotent stem cell (iPSC), and somatic tissue samples. Then loss-of-function experiments in human PSCs were performed to investigate the function of these candidate lncRNAs. The naïve-like pluripotency conversion caused by CCDC144NL-AS1 knockdown (KD) was characterized by quantitative real-time PCR, immunofluorescence staining, western blotting, differentiation of hESCs in vitro and in vivo, RNA-seq, and chromatin immunoprecipitation. Finally, the signaling pathways in CCDC144NL-AS1-KD human PSCs were examined through western blotting and analysis of RNA-seq data. RESULTS: The results indicated that knockdown of CCDC144NL-AS1 induces naïve-like state conversion of human PSCs in the absence of additional transcription factors or small molecular inhibitors. CCDC144NL-AS1-KD human PSCs reveal naïve-like pluripotency features, such as elevated expression of naïve pluripotency-associated genes, increased developmental capacity, analogous transcriptional profiles to human naïve PSCs, and global reduction of repressive chromatin modification marks. Furthermore, CCDC144NL-AS1-KD human PSCs display inhibition of MAPK (ERK), accumulation of active ß-catenin, and upregulation of some LIF/STAT3 target genes, and all of these are concordant with previously reported traits of human naïve PSCs. CONCLUSIONS: Our study unveils an unexpected role of a lncRNA, CCDC144NL-AS1, in the naïve-like state conversion of human PSCs, providing a new perspective to further understand the regulation process of human early pluripotency states conversion. It is suggested that CCDC144NL-AS1 can be potentially valuable for future research on deriving higher quality naïve state human PSCs and promoting their therapeutic applications.

High-spatial-resolution ultrasonic sensor using a micro suspended-core fiber.

A high-resolution fiber-optic ultrasonic sensor based on a suspended-core fiber was designed and experimentally demonstrated. The intrinsic Fabry-Perot interferometer consisting of a micro suspended-core from acid corrosion of a grapefruit fiber proved highly sensitive to a wide range of ultrasonic wave (UW) frequencies. A compact interrogation system using spectral sideband filtering was constructed for UW detection. The sensor exhibited significantly improved spatial resolution and detection sensitivity by etching the suspended-core diameter to few microns. Sensor fabrication involves only fiber splicing and corrosion, which provide a self-shielding cladding surrounding and protecting the core from collisions. This sensor is an excellent candidate for high-quality UW detection.

Compact gas refractometer based on a tapered four-core fiber.

A compact in-line interferometer is proposed and experimentally demonstrated for gas refractive index (GRI) measurement. The sensor comprises a tapered four-core fiber (TFCF) sandwiched between two single-mode fibers (SMFs), forming an in-line SMF-TFCF-SMF structure. The fiber taper acts as a bridge between the external GRI variation and the multimode interference within the TFCF segment. A high sensitivity of 1280.94 dB/refractive index unit is obtained in GRI measurement around 1.0. Temperature change only shifts the interference wavelength, and the cross-sensitivity of temperature can be ignored by intensity demodulation. The proposed gas refractometer, with its improved performance, can be a good candidate for chemical sensing or bio-sensing.

Higher-order micro-fiber modes for Escherichia coli manipulation using a tapered seven-core fiber.

Optical manipulation using optical micro- and nano-fibers has shown potential for controlling bacterial activities such as E. coli trapping, propelling, and binding. Most of these manipulations have been performed using the propagation of the fundamental mode through the fiber. However, along the maximum mode-intensity axis, the higher-order modes have longer evanescent field extensions and larger field amplitudes at the fiber waist than the fundamental mode, opening up new possibilities for manipulating E. coli bacteria. In this work, a compact seven-core fiber (SCF)-based micro-fiber/optical tweezers was demonstrated for trapping, propelling, and rotating E. coli bacteria using the excitation of higher-order modes. The diameter of the SCF taper was 4 µm at the taper waist, which was much larger than that of previous nano-fiber tweezers. The laser wavelength was tunable from 1500 nm to 1600 nm, simultaneously causing photophoretic force, gradient force, and scattering force. This work provides a new opportunity for better understanding optical manipulation using higher-order modes at the single-cell level.

Highly sensitive fiber-optic accelerometer by grating inscription in specific core dip fiber.

A highly sensitive fiber-optic accelerometer based on detecting the power output of resonances from the core dip is demonstrated. The sensing probe comprises a compact structure, hereby a short section of specific core (with a significant core dip) fiber stub containing a straight fiber Bragg grating is spliced to another single-mode fiber via a core self-alignment process. The femtosecond laser side-illumination technique was utilized to ensure that the grating inscription region is precisely positioned and compact in size. Two well-defined core resonances were achieved in reflection: one originates from the core dip and the other originates from fiber core. The key point is that only one of these two reflective resonances exhibits a high sensitivity to fiber bend (and vibration), whereas the other is immune to it. For low frequency (<10 Hz) and weak vibration excitation (<0.3 m/s2) measurement, the proposed sensor shows a much higher resolution (1.7 × 10-3 m/s2) by simply monitoring the total power output of the high-order core mode reflection. Moreover, the sensor simultaneously provides an inherent power reference to eliminate unwanted power fluctuations from the light source and transmission lines, thus providing a means of evaluating weak seismic wave at low frequency.

Spontaneous generation of a novel foetal human retinal pigment epithelium (RPE) cell line available for investigation on phagocytosis and morphogenesis.

OBJECTIVES: Primary retinal pigment epithelium (RPE) cells have a limited capacity to re-establish epithelial morphology and to maintain native RPE function in vitro, and all commercially available RPE cell lines have drawbacks of morphology or function; therefore, the establishment of new RPE cell lines with typical characteristics of RPE would be helpful in further understanding of their physiological and pathological mechanisms. Here, we firstly report a new spontaneously generated RPE line, fhRPE-13A, from a 13-week aborted foetus. We aimed to investigate its availability as a RPE model. MATERIALS AND METHODS: RNA-seq data were mapped to the human genome assembly hg19. Global transcriptional data were analysed by Weighted Gene Co-expression Network Analysis (WGCNA) and differentially expressed genes (DEGs). The morphology and molecular characteristics were examined by immunofluorescence, transmission electron micrographs, PCR and western blot. Photoreceptor outer segments (POS) phagocytosis assay and transepithelial resistance measurement (TER) were performed to assess phagocytic activity and barrier function, respectively. RESULTS: The fhRPE-13A cells showed typical polygonal morphology and normal biological processes of RPE. Meanwhile they were capable of POS phagocytosis in vitro, and the expression level of TYR and TYRP1 were significantly higher than that in ARPE-19 cells. CONCLUSIONS: The foetal human RPE line fhRPE-13A is a valuable system for researching phagocytosis and morphogenesis of RPE in vitro.

Fiber Bragg Grating Sensors for the Oil Industry.

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group's research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors' amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry.

UW Imaging of Seismic-Physical-Models in Air Using Fiber-Optic Fabry-Perot Interferometer.

A fiber-optic Fabry-Perot interferometer (FPI) has been proposed and demonstrated for the ultrasound wave (UW) imaging of seismic-physical models. The sensor probe comprises a single mode fiber (SMF) that is inserted into a ceramic tube terminated by an ultra-thin gold film. The probe performs with an excellent UW sensitivity thanks to the nanolayer gold film, and thus is capable of detecting a weak UW in air medium. Furthermore, the compact sensor is a symmetrical structure so that it presents a good directionality in the UW detection. The spectral band-side filter technique is used for UW interrogation. After scanning the models using the sensing probe in air, the two-dimensional (2D) images of four physical models are reconstructed.

Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion.

A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

Experimental observation of different soliton types in a net-normal group-dispersion fiber laser.

Different soliton types are observed in a net-normal group-dispersion fiber laser based on nonlinear polarization rotation for passive mode locking. The proposed laser can deliver a dispersion-managed soliton, typical dissipation solitons, and a quasi-harmonic mode-locked pulse, a soliton bundle, and especially a dark pulse by only appropriately adjusting the linear cavity phase delay bias using one polarization controller at the fixed pump power. These nonlinear waves show different features, including the spectral shapes and time traces. The experimental observations show that the five soliton types could exist in the same laser cavity, which implies that integrable systems, dissipative systems, and dark pulse regimes can transfer and be switched in a passively mode-locked laser. Our studies not only verify the numeral simulation of the different soliton-types formation in a net-normal group-dispersion operation but also provide insight into Ginzburg-Landau equation systems.

Methylation of RAR-ß2, RASSF1A, and CDKN2A genes induced by nickel subsulfide and nickel-carcinogenesis in rats.

OBJECTIVE: To investigate the expression variation of RAR-ß2, RASSF1A, and CDKN2A gene in the process of nickel-induced carcinogenesis. METHODS: Nickel subsulfide (Ni(3)S(2)) at dose of 10 mg was given to Wistar rats by intramuscular injection. The mRNA expression of the three genes in induced tumors and their lung metastasis were examined by Real-time PCR. The methylation status of the 5' region of these genes were detected by Quantitative Real-time methylation specific PCR. RESULTS: The mRNA expressions of the three genes both in muscle and lung tumor were decreased distinctly in comparison with normal tissue. But hypermethylation was found only in muscle tumor. CONCLUSION: These findings suggest that loss of function or decrease of RAR-ß2, RASSF1A, and CDKN2A, as well as the hypermethylation of 5' region of these genes, are related with nickel exposure.

Effects of miR-541 on neurite outgrowth during neuronal differentiation.

MicroRNA (miRNAs) are short non-coding RNA molecules that downregulate gene expression at post-transcriptional level. miRNAs are post-transcriptional regulators of gene expression important for neuron development and function. This report demonstrated that a putative and chemically synthesized miRNA rno-mir-541 played an important role in the neuron development. Differentiation of PC12 cells with nerve growth factor (NGF) is associated with neurite outgrowth, a process that involves upregulation of Synapsin I. We predicted, detected and assessed the expression levels of a number of possible miRNAs for synapsin I in rats and our outcomes showed that rno-mir-541 was associated with rat synapsin I expression. miR-541, a brain specific miRNA, plays an important role in repressing neurite extension in cultured PC12 neurons. The neurites of PC12 cells was shortened drasticly as a result of the overexpression of rno-mir-541. In contrast, the neurites of PC12 cell developed well after the knockdown of rno-mir-541 by RNA interference. Our study showed that rno-mir-541 played an important role in neuron-cell proliferation and neurite outgrowth through suppressing the expression of its target gene synapsin I. Furthermore, the introduction of NGF causes downregulation of miR-541, de-repression of its target, Synapsin-I and allows for neuritogenesis. Thus, miR-541 functions in neuronal precursors as an endogenous conditional component between NGF and Synapsin-I.

Identification of differentially expressed genes in lung tissues of nickel-exposed rats using suppression subtractive hybridization.

Occupational exposure to nickel compound, such as nickel refining, electroplating, and in conjunction with other metals, is harmful to the health, causing respiratory distress, and lung and nasal cancer. In this work, the different gene expression patterns of lung tissues from nickel-exposed rats and controls were investigated. The suppression subtractive hybridization (SSH) method was used to generate two subtracted cDNA libraries with gene transcripts differentially expressed after nickel inducing. Dot-blot hybridizations were used to confirm differential ratios of expression of obtained SSH clones. Out of 768 unique SSH clones, which were chosen randomly from the two subtraction libraries (384 of each), 319 could be verified as differentially expressed. According to blast screening and functional annotation, 28% genes in nickel-induced cDNA library were related to cell differentiation, whereas 21% in driver library were related to oxygen transport. Two novel expressed sequence tags (ESTs; NCBI Accession No. FC809414 and No. FC809411) in nickel-induced cDNA library were obtained. The genes detected in the present study are probably important genes associated with nickel-induced lung cancer.