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Abstract Background The emergence of multidrug-resistant (MDR) Escherichia coli strains poses significant challenges in clinical settings, particularly when these strains harbor New Delhi metallo-ß-lactamase (NDM) gene, which confer resistance to carbapenems, a critical class of last-resort antibiotics. This study investigates the genetic characteristics and implications of a novel bla NDM-5 -carrying plasmid pNDM-5-0083 isolated from an E. coli strain GZ04-0083 from clinical specimen in Zhongshan, China. Results Phenotypic and genotypic evaluations confirmed that the E. coli ST167 strain GZ04-0083 is a multidrug-resistant organism, showing resistance to diverse classes of antibiotics including ß-lactams, carbapenems, fluoroquinolones, aminoglycosides, and sulfonamides, while maintaining susceptibility to monobactams. Investigations involving S1 pulsed-field gel electrophoresis, Southern blot analysis, and conjugation experiments, alongside genomic sequencing, confirmed the presence of the bla NDM-5 gene within a 146-kb IncFIB plasmid pNDM-5-0083. This evidence underscores a significant risk for the horizontal transfer of resistance genes among bacterial populations. Detailed annotations of genetic elements—such as resistance genes, transposons, and insertion sequences—and comparative BLAST analyses with other bla NDM-5 -carrying plasmids, revealed a unique architectural configuration in the pNDM-5-0083. The MDR region of this plasmid shares a conserved gene arrangement (repA-IS15DIV-bla NDM-5 -ble MBL -IS91-suI2-aadA2-dfrA12) with three previously reported plasmids, indicating a potential for dynamic genetic recombination and evolution within the MDR region. Additionally, the integration of virulence factors, including the iro and sit gene clusters and enolase, into its genetic architecture poses further therapeutic challenges by enhancing the strain’s pathogenicity through improved host tissue colonization, immune evasion, and increased infection severity. Conclusions The detailed identification and characterization of pNDM-5-0083 enhance our understanding of the mechanisms facilitating the spread of carbapenem resistance. This study illuminates the intricate interplay among various genetic elements within the novel bla NDM-5 -carrying plasmid, which are crucial for the stability and mobility of resistance genes across bacterial populations. These insights highlight the urgent need for ongoing surveillance and the development of effective strategies to curb the proliferation of antibiotic resistance.

IntroductionRobotic radical hysterectomy (RRH) is a newly developed minimally invasive surgery that has been suggested as a substitute for laparoscopic radical hysterectomy (LRH). This meta-analysis aims to assess the clinical efficacy and safety of robot-assisted radical hysterectomy (RRH) for cervical cancer.Materials and methodsA systematic search was conducted in four databases (Medline, Embase, Web of Science, and CENTRAL) for studies comparing the utilization of RRH and LRH in the treatment of cervical cancer. The search included articles published from the inception of the databases up until July 18, 2023. Meta-analyses were conducted to assess several surgical outcomes, including operation time, estimated blood loss, length of hospital stay, pelvic lymph nodes, positive surgical margin, total complications, one-year recurrence rate, one-year mortality, and one-year disease-free survival rate.ResultsSix studies were included for meta-analysis. In total, 234 patients were in the RRH group and 174 patients were in the LRH group. RRH had significantly longer operative time (MD=14.23,95% CI:5.27~23.20, P=0.002),shorter hospital stay (MD= -1.10,95% CI:-1.43~0.76, P

The U-shaped fiber configuration represents the elementary form of micro-displacement sensing, characterized by its exceptional freedom and flexibility. The study proposes the U-shaped bent single-mode–multimode–single-mode (SMS) fiber structure that integrates the multimode interference (MMI) effect for enhanced mode dispersion and the Mach–Zönder interference (MZI) effect for spectral sensitivity improvement. The transmission spectral properties of the U-shaped SMS fiber structure with a bent radius over 1 cm are experimentally measured as the change in displacement varied within the range of 5 mm in this work. As the radius decreases, the spectrum shows redshift, which is related to the central wavelength of the peak or dips—a smaller wavelength results in a stronger redshift for the same displacement change. The average sensitivity of micro-displacement measurement within a range of 5 mm is 5.41 pm/μm, and the linearity is 99.62%. The maximum sensitivity of U-shaped SMS fiber structure is 34.46 pm/μm, with the minimum displacement change of approximately 5.804 nm. The transmission spectral properties of the U-shaped SMS fiber structure within the ranges of 50 μm, 500 μm, and 5 mm are experimentally measured in this work. This experiment observed a relatively uniform spectral drift pattern in a large range of micro-displacement sensing. The measurement range is limited by the limited spectral range of the light source and the discontinuous variation in the effective refractive index. This provides an experimental reference for further understanding the characteristics of U-shaped fiber structures and applying its application in micro-displacement sensing.

Abstract Human activity anomaly detection plays a crucial role in the next generation of surveillance and assisted living systems. Most anomaly detection algorithms are generative models and learn features from raw images. This work shows that popular state‐of‐the‐art autoencoder‐based anomaly detection systems are not capable of effectively detecting human‐posture and object‐positions related anomalies. Therefore, a human pose‐driven and object‐detector‐based deep learning architecture is proposed, which simultaneously leverages human poses and raw RGB data to perform human activity anomaly detection. It is demonstrated that pose‐driven learning overcomes the raw RGB based counterpart limitations in different human activities classification. Extensive validation is provided by using popular datasets. Then, it is demonstrated that with the aid of object detection, the human activities classification can be effectively used in human activity anomaly detection. Moreover, novel challenging datasets, that is, BMbD, M‐BMbD and JBMOPbD, are proposed for single and multi‐target human posture anomaly detection and joint human posture and object position anomaly detection evaluations.

Abstract Out-of-plane mechanical properties of the riveted joints restrict the performance of the wing box assembly of airplane. It is necessary to investigate the pull-through performance of the composite/metal riveted joints in order to guide the riveting design and ensure the safety of the wing box assembly. The progressive failure mechanism of composite/aluminum riveted joint subjected to pull-through loading was investigated by experiments and finite element method. A progressive damage model based on the Hashin-type criteria and zero-thickness cohesive zone method was developed by VUMAT subroutine, which was validated by both open-hole tensile test and three-point bending test. Predicted load-displacement response, failure modes and damage propagation were analysed and compared with the results of the pull-through tests. There are 4 obvious characteristic stages on the load-displacement curve of the pull-through test and that of the finite element model: first load take-up stage, damage stage, second load take-up stage and failure stage. Relative error of stiffness, first load peak and second load peak between finite element method and experiments were 8.1%, − 3.3% and 10.6%, respectively. It was found that the specimen was mainly broken by rivet-penetration fracture and delamination of plies of the composite laminate. And the material within the scope of the rivet head is more dangerous with more serious tensile damages than other regions, especially for 90° plies. This study proposes a numerical method for damage prediction and reveals the progressive failure mechanism of the hybrid material riveted joints subjected to the pull-through loading.

The mechanism for the paradox of global warming and successive cold winters in mid-latitudes remains controversial. In this study, the connection between Arctic sea ice (ASI) loss and frequent cold air outbreaks in eastern Continental United States (CONUS) is explored. Two distinct periods of high and low ASI (hereafter high- and low-ice phases) are identified for comparative study. It is demonstrated that cold air outbreaks occur more frequently during the low-ice phase compared to that during the high-ice phase. The polar vortex is weakened and shifted southward during the low-ice phase. Correspondingly, the spatial pattern of 500 hPa geopotential height (GPH), which represents the mid-tropospheric circulation, shows a clear negative Arctic Oscillation-like pattern in the low-ice phase. Specifically, positive GPH anomalies in the Arctic region with two centers, respectively located over Greenland and the Barents Sea, significantly weaken the low-pressure system centered around the Baffin Island, and enhance Ural blocking in the low-ice phase. Meanwhile, the high ridge extending from Alaska to the west coast of North America further intensifies, while the low trough over eastern CONUS deepens. As a result, the atmospheric circulation in North America becomes more conductive to frigid Arctic air outbreaks. It is concluded that the ASI loss contributes to more cold air outbreaks in winter in eastern CONUS through the polar vortex weakening with southward displacement of the polar vortex edge, which lead to the weakening of the meridional potential vorticity gradient between the Arctic and mid-latitude and thus are conducive to the strengthening and long-term maintenance of the blocking high.

Adenosine is a vital biological small molecule that regulates various physiological processes in the human body. A high expression of adenosine in cells can facilitate tumor growth. Therefore, detecting adenosine is crucial for early disease diagnosis. In this paper, we designed a fluorescent biosensor for the sensitive detection of adenosine based on the cationic comb-type copolymer PLL-g-Dex for assisted rapid hybridization of nucleic acids at room temperature. In this strategy, adenosine preferentially binds to the aptamer immobilized on the surface of magnetic nanobeads, releasing free aDNA in solution as the primer strand, which rapidly forms DNA nanowires with auxiliary probes of bDNA with the assistance of PLL-g-Dex. SYBR Green I is embedded in DNA duplexes to generate strong fluorescence. The experimental results showed that PLL-g-Dex promotes DNA hybridization reactions at room temperature to form ultra-long DNA nanowires, thus achieving signal amplification and shortening the detection time. In addition, magnetic nanobeads can reduce the background signal during the reaction. Compared with several previous studies on the fluorescence detection of adenosine, this strategy has a lower detection limit of 2.32 nM. Furthermore, this novel system exhibited a good detection performance even under complex environments, such as serum, providing some reference for the quantitative detection of adenosine in early disease diagnosis.

BackgroundConventional systemic inflammatory biomarkers could predict prognosis in patients with ischemic stroke (IS) admitted to the intensive care unit (ICU). Acute kidney injury (AKI) is common in patients with IS admitted to ICU, but few studies have used systemic inflammatory biomarkers to predict AKI in critically ill patients with IS. This study aimed to establish a risk model based on white blood cell (WBC)-related biomarkers to predict AKI in critically ill patients with IS.MethodsData were extracted from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) for a training cohort, and data were extracted from the Medical Information Mart for eICU Collaborative Research Database (eICU-CRD) for a validation cohort. Logistic regression analysis was used to determine the significant predictors of WBC-related biomarkers on AKI prediction, and a risk model was established based on those significant indicators in multivariate logistic regression. The receiver operating characteristics (ROC) curve was utilized to obtain the best cut-off value of the risk model. The Kaplan–Meier curve was used to evaluate the prognosis-predictive ability of the risk model.ResultsThe overall incidence of AKI was 28.4% in the training cohort and 33.2% in the validation cohort. WBC to lymphocyte ratio (WLR), WBC to basophils ratio (WBR), WBC to hemoglobin ratio (WHR), and neutrophil to lymphocyte ratio (NLR) could independently predict AKI, and a novel risk model was established based on WLR, WBR, WHR, and NLR. This risk model depicted good prediction performance both in AKI and other clinical outcomes including hemorrhage, persistent AKI, AKI progression, ICU mortality, and in-hospital mortality both in the training set and in the validation set.ConclusionA risk model based on WBC-related indicators exhibited good AKI prediction performance in critically ill patients with IS which could provide a risk stratification tool for clinicians in the ICU.

At present, a large number of studies have demonstrated that miRNAs can be used as biological indicators for the diagnosis and treatment of diseases such as tumours and cancer, so it is important to develop a new miRNA detection platform. In this work, miRNA-122 is used as the basis for targeting detection agents. We have designed an unlabelled DNA1 that undergoes partial hybridisation and has a 20 T base long strand. The fluorescent signal in this experiment is derived from copper nanoclusters (CuNCs) generated on the circular T-long strand of DNA1. At the same time, DNA1 is able to react with miRNA-122 and achieve hydrolysis of the part bound to miRNA-122 via the action of nucleic acid exonuclease III (Exo III), leaving a part of the DNA, called DNA3, while releasing miRNA-122 to participate in the next reaction, thus achieving circular amplification. DNA3 is able to react with DNA2, which is bound to streptavidin magnetic beads (SIBs) and separated from the reaction solution via the application of a magnetic field. Overall, this is a fluorescence signal reduction experiment, and the strength of the fluorescence signal from the copper nanoclusters can determine whether the target miRNA-122 is present or not. The degree of fluorescence reduction indicates how much DNA1, and thus the amount of target miRNA-122, has been hydrolysed. By evaluating the variations in the fluorescence signal under optimised conditions, we discovered that this method has good sensitivity, with a detection limit as low as 0.46 nM, better than many other previous works on fluorescence signal-based biosensors for miRNA detection. This technique offers high discrimination and selectivity and can serve as a persuasive reference for early diagnosis.

Cervical cancer is an important topic in the study of global health issues, ranking fourth among women’s cancer cases in the world. It is one of the nine major cancers that China is focusing on preventing and treating, and it is the only cancer that can be prevented through vaccination. Systematic and effective screening for human papilloma (HPV) infection, which is closely linked to the development of cervical cancer, can reduce cervical cancer incidence and mortality. In this paper, an electrochemical sensor was designed to detect HPV 16 using dual-signal amplification. An APTES-modified glassy carbon electrode was used for improved stability. Gold nanoparticles and a chain amplification reaction were combined for signal amplification. The limit of detection (LOD) of this electrochemical sensor was 1.731 × 10−16 mol/L, and the linear response of the target detector range was from 1.0 × 10−13 mol/L to 1.0 × 10−5 mol/L (R2 = 0.99232). The test of serum sample recovery showed that it has good anti-interference, and the performance of all aspects was improved to different degrees compared with the previous research from the team. The designed sensor is centered around the principles of low cost, high sensitivity and stability, which provides new ideas for the future development of cervical cancer prevention and electrochemical biosensors.

Because microRNAs (miRNAs) are biological indicators for the diagnosis, treatment, and monitoring of tumors, cancers, and other diseases, it is significant to develop a rapid, sensitive, and reliable miRNA detection platform. In this study, based on miRNA-21 detection, DNA-a with a 3′ end overhang and Texas Red fluorophore-labeled 5′ end was designed, which reacts with miRNA-21 and hybridizes with exonuclease III (Exo III), where the part connected to miRNA-21 is hydrolyzed, leaving a-DNA. At the same time, miRNA-21 is released to participate in the following reaction, to achieve cyclic amplification. a-DNA reacts with DNA-b conjugated to gold nanoparticles to achieve fluorescence quenching, with the quenching value denoted as F; additionally, after adding DNA-d and linked streptavidin immunomagnetic beads (SIBs), fluorescence recovery was achieved using DNA-c, with the recovered fluorescence recorded as F0. By comparing the difference in the fluorescence (F0 − F) between the two experiments, the amount of DNA-a hydrolyzed to produce a-DNA was established to determine the target miRNA-21 content. Under optimized conditions, by comparing the changes in the fluorescence signal, the developed strategy shows good sensitivity and repeatability, with a detection limit of 18 pM, good discriminative ability and selectivity, and promise for the early diagnosis of breast and intestinal cancers.

Given a bug report, bug localization technique can help developers automatically locate potential buggy files. Information retrieval and deep learning approaches have been applied in bug localization by extracting lexical features in bug reports and syntactic features in source code files, though they fail to utilize the structural and semantic information of source code files. In this paper, we present a bug localization system CAST, which exploits deep learning and customized abstract syntax trees of programs to locate potential buggy source files automatically and effectively. Specifically, CAST extracts both lexical semantics in bug reports (e.g., words) and source files (e.g., method names) and program semantics in source files (e.g., abstract syntax tree, AST). Moreover, CAST enhances the tree-based convolutional neural network (TBCNN) model with customized ASTs, which distinguish between user-defined methods and system-provided ones to reflect their contributions leading to defects. Furthermore, customized ASTs group the syntactic entities with similar semantics and prune the ones with little or redundant semantics in order to facilitate the learning performance. Experimental results on four widely-used software projects show that CAST significantly outperforms the state-of-the-art methods in locating the buggy source files.

Lubricating oil can effectively reduce friction between mechanical parts, thereby reducing energy consumption and improving service life and reliability. Due to the development of science and technology, it is necessary to improve the performance of lubricating oil to fulfill the higher tribological requirements for countering wear and providing lubrication. Nanolubricant additives have the four lubrication mechanisms of micro-bearing, protective film, polishing, and repair effects. A nanolubricant additive can often demonstrate a variety of lubrication mechanisms at the same time. As lubricating additives, metal and metal oxide nanoparticles have outstanding effects which improve the tribological properties of lubricating oil and have been widely studied in the field of tribology. This paper introduces the lubrication mechanism of nanoadditives and the latest research results for metal and metal-oxide nanoparticle lubrication additives.

Coupled general circulation models (CGCMs), as tools of predicting climate variability, are constantly being improved due to their immense value in a host of theoretical and practical, real-world problems. Consequently, four new parameterization schemes are introduced in the First Institute of Oceanography Earth System Model (FIO-ESM), and a new climate prediction System (CPS) is built up based on modified and original FIO-ESM. Here, turbulence from the sea surface to deep ocean were fully described, and seasonal forecasts of El Niño-Southern Oscillation (ENSO) and year-to-year prediction of Pacific Decadal Oscillation (PDO) were made with both the modified and original FIO-ESM-CPS. The results illustrate that the anomaly correlation coefficient (ACC) of the Niño 3.4 index significantly increased, and the root mean square error (RMSE) significantly decreased, respectively, in the modified FIO-ESM-CPS as compared to the original. The RMSE is improved by over 20% at 4- and 5-month lead times. Over longer leads, and in the modified FIO-ESM-CPS, forecast ENSO amplitudes are far closer to observations than the original CGCM, which significantly overestimates amplitudes. PDO prediction skill is also improved in the modified FIO-ESM-CPS with ACC improving by 36% at the 4-year lead time and RMSE decreasing by 21% at the 3-year lead time.

High-risk human papillomavirus (HPV) infection is an important cause of cervical cancer formation; therefore, being able to detect high-risk HPV (e.g., HPV-16) is important for the early treatment and prevention of cervical cancer. In this study, a combination of a 3-aminopropyltriethoxysilane (APTES) modified gold electrode and a super sandwich structure was creatively developed, resulting in the development of a biosensor that is both sensitive and stable for the detection of HPV-16. The electrochemical biosensor possesses a lower detection limit compared with previous studies with an LOD of 5.475 × 10−16 mol/L and it possesses a wide linear range from 1.0 × 10−13 mol/L to 1.0 × 10−6 mol/L (R2 = 0.9923) for the target DNA. The experimental data show that the sensor has good stability, and there is no significant decrease in the current response value after 7 days in the low-temperature environment. In addition, the sensor proved to be a powerful clinical tool for disease diagnosis because it showed good interference resistance in complex human serum samples.

A progressive damage model for aramid honeycomb cutting was proposed to reveal its cutting damage mechanism. It established the relationship between the mesoscale failure modes and the macroscale cutting damage types of the aramid honeycomb. The proposed model addressed the material assignment problem of impregnated honeycomb by developing a material calculation method that simulates the real manufacturing process of the aramid honeycomb. Cutting experiment of aramid honeycomb specimen was conducted concerning on the cutting forces response and cutting damages, which validated that the proposed method was effective for investigating the cutting process and mechanism for the aramid honeycomb. Predicted cutting mechanism results show that: (a) cutting process of the aramid honeycomb can be divided into three stages with four characteristic states—initial state, cut-in state, cut-out state and final state; (b) cell wall bending in the cutting direction relieves the cutting force, and strong plasticity of the aramid fiber makes it hard to break, which lead to uncut fiber and burr damages; (c) using sharp tip cutting tool to reduce cutting force and bonding both top and bottom of the honeycomb to make it stiffer are beneficial to obtain good cutting quality with less damages.

Vascular endothelial growth factor (VEGF) is a critical biomarker in the angiogenesis of several cancers. Nowadays, novel approaches to rapid, sensitive, and reliable VEGF detection are urgently required for early cancer diagnosis. Cationic comb-type copolymer, poly(L-lysine)-graft-dextran (PLL-g-Dex) accelerates DNA hybridization and chain exchange reaction while stabilizing the DNA assembly structure. In this work, we examined the chaperone activity of PLL-g-Dex to assist G-quadruplex-based fluorescent DNA biosensors for sensitive detection of VEGF. This convenient and effective strategy is based on chitosan hydrogel, c-myc, Thioflavin T (ThT), VEGF aptamer, and its partially complementary strand. The results show that chaperone copolymer PLL-g-Dex significantly promotes the accumulation of G-quadruplex and assembles into G-wires, allowing an effective signal amplification. Using this method, the detection limit of VEGF was as low as 23 pM, better than many previous works on aptamer-based VEGF detection. This chaperone copolymer-assisted signal amplification strategy has potential applications in the highly sensitive detection of target proteins, even including viruses.

Although miRNAs exist in small quantities in the human body, they are closely related to the abnormal expression of genes in diseases such as tumors. Therefore, sensitive detection of miRNAs is very important for the prevention and treatment of various tumors and major diseases. The purpose of this study is to develop a label-free sensing strategy based on the co-action of double-hairpin molecular beacons and deoxyribozymes (DNAzymes) for highly sensitive detection of miRNA-21. The target miRNA-21 promotes the assembly of DNAzyme with a complete catalytic core region. At the presence of Mg2+, DNAzyme cuts a substrate into short chains, which open the double hairpin molecular beacon, and then form G-quadruplexs at both ends, specifically binding more ThT to generate a amplified fluorescent signal. The cut substrate will be replaced by the uncut ones in the next stage, increasing the concentration of reactants, and thus further improving the fluorescence intensity. This DNAzyme assisted double hairpin molecular beacon has a certain degree of discrimination for substances with single base mismatches, and the detection limit of miRNA-21 is 0.13 pM, lower than that of the many other analysis. Further, this detection has good selectivity and sensitivity in serum. Therefore, this strategy provides a simple, fast and low-cost platform for the sensitive detection of miRNA-21, having potential applications in early cancer diagnosis.

As a prime circulation system, the western Pacific subtropical high (WPSH) significantly impacts tropical cyclone (TC) activities over the western North Pacific (WNP), especially TCs landing on the east coast of China; however, the associated mechanism is not firmly established. This study investigates the underlying dynamic impact of the first two empirical orthogonal function (EOF) modes of the WPSH on the interannual variability in the genesis and number of TCs landing over the WNP. The results show that these two dominant modes control the WNP TC activity over different subregions via different environmental factors. The first mode (EOF1) affects the TC genesis number over region I (105°–128° E, 5°–30° N) (r = −0.49) and region II (130°–175° E, 17°–30° N) (r = −0.5) and controls the TCs landing on the east coast of China, while the second mode (EOF2) affects the TC genesis number over region III (128°–175° E, 5°–17° N) (r = −0.69). The EOF1 mode, a southwest-northeast-oriented enhanced pattern, causes the WPSH to expand (retreat) along the southwest-northeast direction, which makes both mid-low-level relative humidity and low-level vorticity unfavorable (favorable) for TC genesis in region I and region II and steers fewer (more) TC tracks to land on the coast of China. The EOF2 mode features a strengthened WPSH over the southeast quarter of the WNP region. The active (inactive) phases of this mode control the low-level vorticity and vertical wind shear in region III, which lead to less (more) TC genesis over this region. The prediction equations combining the two modes of the WPSH for the total number of TCs and TCs that make landfall show high correlation coefficients. Our findings verify the high prediction skill of the WPSH on WNP TC activities, provide a new way to predict TCs that will make landfall on the east coast of China, and help to improve the future projection of WNP TC activity.

The qualitative and quantitative determination of marker protein is of great significance in the life sciences and in medicine. Here, we developed an electrochemical DNA biosensor for protein detection based on DNA self-assembly and the terminal protecting effects of small-molecule-linked DNA. This strategy is demonstrated using the small molecule biotin and its receptor protein streptavidin (SA). We immobilized DNA with a designed structure and sequence on the surface of the gold electrode, and we named it M1-Biotin DNA. M1-Biotin DNA selectively combines with SA to generate M1-Biotin-SA DNA and protects M1-Biotin DNA from digestion by EXO III; therefore, M1-Biotin DNA remains intact on the electrode surface. M1-Biotin-SA DNA was modified with methylene blue (MB); the MB reporter molecule is located near the surface of the gold electrode, which generates a substantial electrochemical signal during the detection of SA. Through this strategy, we can exploit the presence or absence of an electrochemical signal to provide qualitative target protein determination as well as the strength of the electrochemical signal to quantitatively analyze the target protein concentration. This strategy has been proven to be used for the quantitative analysis of the interaction between biotin and streptavidin (SA). Under optimal conditions, the detection limit of the proposed biosensor is as low as 18.8 pM, and the linear range is from 0.5 nM to 5 μM, showing high sensitivity. The detection ability of this DNA biosensor in complex serum samples has also been studied. At the same time, we detected the folate receptor (FR) to confirm that this strategy can be used to detect other proteins. Therefore, this electrochemical DNA biosensor provides a sensitive, low-cost, and fast target protein detection platform, which may provide a reliable and powerful tool for early disease diagnosis.

A hybrid double cladding erbium–ytterbium co-doped fiber (EYDF) amplifier with a single-mode-multimode-single-mode (SMS) active fiber is demonstrated in this study. The hybrid gain fiber with an SMS structure is composed of two kinds of EYDFs with 6 and 12 μm core diameters. The transmission spectra of the SMS fiber structure were theoretically analyzed and the simulation results indicated that the maximum loss in the 1~1.1 μm band where the Yb-band amplified spontaneous emission (Yb-ASE) located, was much larger than that of the 1.5-μm band because of the wavelength difference. The power performance and spectra properties of the hybrid fiber amplifier were theoretically and experimentally analyzed and compared with a typical uniform fiber amplifier under the same conditions. The experimental results demonstrated that this hybrid fiber amplifier can suppress the Yb-ASE by over 12 dB and increase the slope efficiency by more than 2%, but the ASE in the 1.5-μm band increases by 2~3 dB. This work provides a possible method to enable EYDF amplifiers to suppress the Yb-ASE and overcome the pump bottleneck effect.

A microRNA (miRNA) detection platform composed of a rolling circle amplification (RCA) system and an allosteric deoxyribozyme system is proposed, which can detect miRNA-21 rapidly and efficiently. Padlock probe hybridization with the target miRNA is achieved through complementary base pairing and the padlock probe forms a closed circular template under the action of ligase; this circular template results in RCA. In the presence of DNA polymerase, RCA proceeds and a long chain with numerous repeating units is formed. In the presence of single-stranded DNA (H1 and H2), multi-component nucleic acid enzymes (MNAzymes) are formed that have the ability to cleave substrates. Finally, substrates containing fluorescent and quenching groups and magnesium ions are added to the system to activate the MNAzyme and the substrate cleavage reaction, thus achieving fluorescence intensity amplification. The RCA–MNAzyme system has dual signal amplification and presents a sensing platform that demonstrates broad prospects in the analysis and detection of nucleic acids.

This paper focuses on the fatigue reliability analysis and the development of a new life model of reliability and crack growth mechanisms in FV520B-I (high strength martensitic-type stainless steels) in the very-high cycle fatigue (VHCF) regime, which haven’t been studied well. First, the fatigue test was carried out to clarify the fatigue failure mechanism in the very-high cycle regime. Based on the test results and fatigue reliability theory, the fatigue life distribution and P-S-N curves were modeled. A new fatigue life evaluation model for FV520B-I is proposed according to the fracture mechanics and classic life evaluation method. With the comprehensive application of P-S-N curves and a new proposed fatigue life evaluation model, a new assumption of a P-Sc-N curve is developed and verified, to quantitatively express the relationship between fatigue life, reliability and fatigue cracking. This is novel and valuable for further fatigue study of FV520B-I.