Search Results (57)

In this study, we developed a multiplex one-tube nested real-time fluorescent quantitative PCR (mONRT-PCR) assay integrated with a portable, fully automated nucleic acid point-of-care testing (POCT) platform for the detection of Haemophilus influenzae (H. influenzae), Listeria monocytogenes (L. monocytogenes), and Cryptococcus neoformans (C. neoformans) in cerebrospinal fluid (CSF). The assay enables nested amplification within a closed system using conventional primers and probes, thereby reducing operational complexity and minimizing contamination risk. Analytical evaluation demonstrated limits of detection of 10⁰ copies/μL for H. influenzae and L. monocytogenes, and 10¹ copies/μL for C. neoformans using recombinant plasmids, as well as 10⁻⁷ to 10⁻⁶ ng/μL using genomic DNA. No cross-reactivity was observed when tested against a panel of 17 common non-target microorganisms encountered in clinical microbiology laboratories. In simulated CSF samples, the assay maintained detectable amplification at low pathogen concentrations. When implemented on the POCT platform, detection limits reached 5, 10, and 50 CFU/mL for the three pathogens, respectively. Clinical evaluation using 43 CSF samples showed almost perfect agreement with conventional qPCR (κ = 0.861, p < 0.001). Notably, additional C. neoformans detections were observed by mONRT-PCR-POCT compared with qPCR, suggesting improved sensitivity under clinical conditions. The assay yielded results within approximately 1 h and 47 min. These findings indicate that the proposed assay provides a rapid, sensitive, and integrated approach for meningitis pathogen detection, while maintaining a practical balance between analytical performance and operational simplicity. Further validation in larger cohorts is warranted. Full article

Bloodstream infections (BSI) carry high mortality, but traditional blood culture is too slow for urgent clinical needs. This study aims to develop a rapid point-of-care testing assay based on one-tube multiplex nested polymerase chain reaction (PCR) (OM-NPCR-POCT) for early diagnosis of three pathogens in bloodstream infection patients: Escherichia coli (ECO), Klebsiella pneumoniae (KPN), and Streptococcus pneumoniae (SPN). The analytical sensitivity of the one-tube multiplex nested PCR (OM-NPCR) was evaluated using recombinant bacterial plasmids. The analytical sensitivity of the OM-NPCR-POCT assay was assessed using simulated samples. The clinical performance was evaluated in 90 clinical blood samples, with results compared to conventional quantitative PCR (qPCR). Finally, the agreement between the two detection methods was assessed via Kappa analysis. The limits of detection (LODs), calculated from serial dilution experiments, were 4, 2, and 1 copies/μL for plasmids ECO, KPN, and SPN, respectively. The OM-NPCR-POCT assay achieved LODs of 20, 10, and 10 CFU/mL for ECO, KPN, and SPN in simulated samples, with a total testing time of approximately 2 h. The clinical evaluation of OM-NPCR-POCT demonstrates consistency with conventional qPCR while exhibiting higher sensitivity. This method has potential as a rapid diagnostic tool for early bloodstream infection detection. Full article

A novel anti-resonant hollow-core fiber (AR-HCF) is proposed. The fiber uses cross-nested circular cladding tubes including single-nested and non-nested tubes in the near-infrared spectral region of 1.3–1.7 μm. All the anti-resonant tubes are used to minimize the confinement loss (CL) of the LP₀₁ core mode. The non-nested tubes are also employed to achieve single-mode performance through strong mode coupling between the cladding mode and the LP₁₁ core mode. The impact of the structural parameters on the CL of the modes is analyzed by using the finite element method (FEM). Optimization results indicate that the CLs of the LP₀₁ mode and the LP₁₁ mode are 0.18 dB/km and 5.88 × 10³ dB/km at 1.55 μm. Consequently, the higher-order mode extinction ratio (HOMER) achieves 3.27 × 10⁴. Additionally, the mode field area of the fiber exceeds 4720 μm² and the corresponding mode field diameter of the LP₀₁ mode is more than 77 μm across the spectral region of 1.3–1.7 μm. In the practical applications, the fabrication tolerance is analyzed. The collapse of anti-resonant tubes within 0–2 μm and positional offsets between 0° and 4° both have minimal impact on fiber performance, thereby ensuring the stability of the system. Compared with other reported fibers, the proposed fiber demonstrates superior performance. Full article

Spring viremia of carp (SVC) is a highly contagious disease that affects cyprinids, resulting in systemic hemorrhage, abdominal distension, exophthalmia, and high mortality in juveniles. This can lead to significant losses in the aquaculture industry. The World Organization for Animal Health (WOAH) recommends a two-step semi-nested reverse transcription polymerase chain reaction (RT-PCR) method for diagnosis. However, this method is labor-intensive, requires large reagent volumes, and is prone to carry-over contamination. Here, we evaluated the detection sensitivity of one-step semi-nested RT-PCR (combining RT and primary amplification in a single tube, followed by a second nested PCR step) against conventional two-step semi-nested RT-PCR. SVC virus (SVCV) subgroup Ia was tested using cell culture, RT-quantitative PCR, and one-step RT-PCR. The two-step semi-nested PCR method detected viral RNA up to a 10⁻² dilution, whereas one-step semi-nested RT-PCR detected it up to a 10⁻⁵ dilution, showing a 1000-fold improvement in sensitivity. Moreover, detection rates increased from 84.2% with two-step semi-nested RT-PCR to 91.7% with one-step semi-nested RT-PCR in fish tissue samples. One-step semi-nested RT-PCR reduces processing time, minimizes handling steps, and contamination risk, and enhances analytical sensitivity. This supports its adoption as a practical, high-throughput diagnostic tool for SVCV and consideration for future WOAH guidelines. Full article

A nested semi-tube hollow-core anti-resonant fiber (HC-ARF) that can support the high-purity transmission of a few polarization-maintaining modes is designed in this paper. By employing bi-thickness hybrid silica/silicon anti-resonant tubes, the birefringence of the orthogonal polarized modes is significantly improved, and the weak coupling condition of the five lowest-order polarization maintaining modes, including the LP_{01_x}, LP_{01_y}, LP_{11a_x}, LP_{11b_x}, and LP_{11a_y}, can be met. The effective refractive index difference between each pair of the supported adjacent modes is larger than 1.0 × 10⁻⁴. With hybrid multi-layer nested semi-tubes, the confinement losses of the supported modes are all less than 1.50 × 10⁻¹ dB/m within a transmission band from 1.530 to 1.620 μm. The minimum confinement losses of the LP_{01_y}, LP_{01_x}, LP_{11a_y}, LP_{11a_x}, and LP_{11b_x} modes are 3.71 × 10⁻⁴ dB/m, 1.61 × 10⁻³ dB/m, 2.00 × 10⁻² dB/m, 1.30 × 10⁻¹ dB/m, and 4.20 × 10⁻² dB/m, respectively. Meanwhile, the unwanted higher-order modes are filtered out well to guarantee the modal purity. The minimum higher-order-mode extinction ratio of the lowest-loss LP₂₁ mode to the highest-loss LP₁₁ mode remains larger than 139 from 1.545 to 1.615 μm. The numerical results highlight the potential of the proposed polarization-maintaining few-mode hollow-core anti-resonant fibers in many application fields, such as short-range and high-capacity data transmission networks, fiber sensing systems, quantum communication systems, and so on. Full article

To address the issues of limited orbital angular momentum (OAM) mode count, poor transmission quality, and complex cladding structures in ring-core photonic crystal fibers, a novel OAM-supporting ring-core anti-resonant photonic crystal fiber is designed. This fiber features a high-index-doped ring-core surrounded by a three-layer anti-resonant nested tube cladding. Numerical simulations based on the finite element method indicate that the designed fiber has the ability to reliably transmit up to 90 OAM modes within the wavelength range of 1530–1620 nm. Additionally, this fiber demonstrates outstanding performance characteristics, achieving a peak effective refractive index difference of 0.0041 while maintaining remarkably low confinement loss between 10⁻¹² dB/m and 10⁻⁸ dB/m. The minimum effective mode field area is 101.41 μm², and the maximum nonlinear coefficient is 1.05 W⁻¹·km⁻¹. The dispersion is flat, with a minimum dispersion variation of merely 0.5394 ps/(nm·km). The mode purity is greater than 98.5%, and the numerical aperture ranges from 0.0689 to 0.089. The designed OAM-supporting ring-core anti-resonant photonic crystal fiber has broad application prospects in long-haul optical communication and high-speed data transmission. Full article

At present, most studies in the field of Wire-Friction Stir Additive Manufacturing (W-FSAM) adopt the side wire feeding method. However, the side wire feeding method has problems in that the wire feeding tube occupies working space and the tool is prone to clogging. To address this, this study proposes a Coaxial Wire Feeding-Friction Stir Additive Manufacturing (CWF-FSAM) method. The CWF-FSAM device adopts a structure where a fixed shaft is coaxially nested inside the stirring shaft, and the fixed shaft is machined with through-channels along the circumferential direction for wire feeding, which eliminates the limitation of the wire feeding tube. This study elaborates on the structure of the CWF-FSAM device, then uses 6061 aluminum alloy as the deposition material for additive manufacturing, and conducts characterization and analysis on the microstructure and mechanical properties of the deposited components. The results show that the interlayer bonding of the deposited components is dense without defects. The components exhibit uniform and fine equiaxed grains, with the average grain sizes of the top, middle, and bottom parts being 3.52 µm, 3.35 µm, and 4.07 µm, respectively. In terms of mechanical properties, the tensile strengths of the components along the building direction (BD) and longitudinal direction (LD) both reach 70% of that of the base material (BM) wire. The hardness ranges from 36 HV to 42 HV. In addition, closed-loop components were prepared by continuous counterclockwise deposition using the CWF-FSAM device. The tensile strengths of the overlapping area, straight section, and corner were 124.45 MPa, 125.88 MPa, and 126.95 MPa, respectively. The overall performance of the closed-loop components is uniform and stable, which indicates that the CWF-FSAM-deposited components have good mechanical property isotropy. Full article

The incidence of fire accidents resulting from refrigerant leaking following the rupture of air conditioning condenser tubes has escalated in recent years. Corrosion from carboxylic acid is a primary cause in the rupture of copper tubes. The influence of lubricating oil and iron filings generated by the wear of air conditioning compressors on the corrosion of condenser copper tubes is rarely mentioned in the existing research. In order to simulate the environmental conditions inside the air conditioning unit, this study utilizes acetic acid vapor to corrode copper tubes and explores the effects of lubricating oil and iron powder on copper tube corrosion. The results demonstrate that copper corrosion follows a dendritic corrosion pattern, achieving a maximum depth of 51 μm after 28 days in 1% acetic acid vapor. A small amount of copper hydroxy acetate appears in the early stage. Copper hydroxy acetic and basic carbonate copper are converted into acetic acid copper hydrate as the acetic acid vapor increases over time. The ultimate products appear as turquoise-blue crystals. POE lubricant diminishes the corrosion rate by establishing an oil layer barrier that mitigates the volatilization of acetic acid. Iron powder preferentially reacts with acetic acid to initially protect the copper tube. The Fe³⁺ produced oxidizes the copper in acetic acid, hence the concentration of copper acetate rises, which facilitates the crystallization of copper acetate. Full article

Anthropogenic environments are increasingly recognised for their potential to support pollinator diversity, especially through the strategic selection of ornamental plant species. This study investigated the ecological role of Salvia yangii (formerly Perovskia atriplicifolia) in supporting solitary bees, particularly species of the genus Anthidium, within urban green spaces in Milan (Italy). Field observations were conducted in both urban and rural sites to assess pollinator visitation rates, bee abundance, and plant traits relevant to nesting and foraging. S. yangii attracted a diverse assemblage of bee genera, with Anthidium spp. consistently recorded as dominant visitors. This preference is likely driven by the short corolla tube, which facilitates the access to nectar, and its dense coverage of trichomes, which may serve as essential nesting materials. The interaction was found to be stable across environments, suggesting that S. yangii provides reliable floral and structural resources. These findings highlight the potential of specific ornamental plants to contribute meaningfully to urban pollinator conservation. While the use of exotic species warrants caution, we propose that S. yangii may be suitable for inclusion in pollinator-friendly planting guidelines under controlled horticultural conditions, offering a promising model for enhancing urban biodiversity through informed plant selection. Full article

Background: Congenital anomalies impact 52 million infants worldwide with an estimated 94% living in low- and middle-income countries (LMICs). Approximately 200,000 children are born with a neural tube defect (NTD) in LMICs annually. Zambia is an LMIC with a high burden of myelomeningocele (MMC; a severe form of NTD). This study sought to characterize the barriers influencing access to healthcare for children born with MMC in Zambia. Methods: Two cross-sectional surveys were administered to healthcare providers at referring public health facilities and mothers of infants born with MMC undergoing surgical closure. The survey among mothers was nested in a longitudinal study evaluating surgical closure in Lusaka, Zambia from 28 May 2024 to 21 January 2025. Results: Sixty-nine mother–MMC baby dyads and 123 providers from 21 facilities were enrolled in the study. The median age at presentation for MMC was 7.5 (range 0–244) days old. Most patients were referred from rural district hospitals (51%; n = 35) and travelled greater than 250 km to access care (80%; n = 55). Seventy-seven percent (n = 53) of mothers reported receiving at least one antenatal ultrasound, with 62% (n = 43) undergoing an ultrasound after 20 weeks estimated gestational age. Of these, only 3% (n = 2) received an MMC diagnosis prior to delivery. Referring patients with MMC for further care greater than six hours after birth was reported by 59% providers (n = 73). Hospitals further away from the tertiary center were more likely to report late referrals (p < 0.001). Conclusions: There is a delay in the diagnosis and referral of infants with MMC to specialized care in Zambia, which may be attributed to inadequate in utero diagnosis capabilities and distance from the tertiary facility. Improving the accuracy of prenatal diagnosis and strengthening referral pathways to facilitate access to care among infants with MMC in Zambia are important for improving incidence and outcomes. Full article

Megachilidae are crucial pollinators of cultivated and wild vegetation, playing a vital role in ecosystem pollination services, however, there is still a lack of information regarding the ecology and behavior of these species. This study aims to analyze the nesting ecology strategies of four sympatric species of leafcutting bees and their interactions with pollen source plants. Data were collected from April to October from 2019 to 2022 in the Jiyuan section of the Taihang Mountain National Nature Reserve (approximately 35°10′–35°25′ N, 111°55′–112°10′ E) using trap nest methods. Through the dissection of nesting tubes, their structural characteristics were revealed, and the pollen sources collected by the bees were identified. Our results showed that nesting activity of leafcutting bees lasted from May to October, with a preference for nesting tubes of 6 to 10 mm in diameter and 131 to 170 mm in length. We documented 48 plant species used as foraging sources, belonging to 17 orders, 24 families, and 33 genera, with the Fagaceae family (9 species) being predominant. The results indicate that the distinctive traits of these species—such as the asynchronous nesting periods, the types of nesting materials, the dimensions of cavities, and differential utilization of floral resources—likely play a critical role in niche differentiation among sympatric species, thereby ensuring the maintenance and persistence of Megachilidae populations in this region. Full article

We propose a new hollow-core fiber design based on a hybrid structure of nested elliptical and semicircular tubes. We numerically investigate the loss and single-mode performance of this design in the communication band and derive the values of each parameter of the fiber cladding structure that theoretically lead to the best performance of the fiber. The resulting structure has a minimum confinement loss as low as 0.00033 dB/km at 1550 nm and an astonishing extinction ratio of 2,439,607 for the higher-order modes, showing excellent loss and single-mode performance. In addition, the design also exhibits excellent bending insensitivity, with the loss gradually dropping well below 0.01 dB/km when the bending radius exceeds 14 cm. The proposed fiber structure has a very promising application in optical communication systems. Full article

A novel nested structure of hollow-core anti-resonant optical fiber is proposed to achieve low loss, large effective mode area, and wide transmission band simultaneously in the near-infrared range of 1200–2200 nm. It is composed of six elliptical cladding tubes nested with six large circular cladding tubes, and six small circular cladding tubes are introduced in the gap of the elliptical tubes. The transmission characteristics of the hollow-core anti-resonant optical fiber are numerically investigated using the full-vector finite element method. The effects of structural parameters such as the cladding tube thickness and the tube diameters on the fiber transmission characteristics are analyzed in detail. The results indicate that within the wavelength range of 1200–2200 nm, the confinement loss remains below 0.017 dB/km, and the minimum confinement loss can be as low as 1.2 × 10⁻⁴ dB/km at 1500 nm. The effective mode area remains as large as ~1142.5 μm². It should be noted that in the wide wavelength range of 1000 nm, the dispersion exhibits excellent characteristics ranging from 0.7 to 1.4 ps/(nm·km). Our fiber can find potential applications in ultra-long-distance and ultra-high-power transmission systems with a wide operating wavelength band. Full article

Rickettsiae are Gram-negative and obligate intracellular bacteria that cause rickettsioses. These pathogens are typically transmitted by arthropod vectors, such as ticks, mesostigmatid mites, and fleas. Rickettsiae are responsible for many emerging infectious diseases worldwide and are the second most frequently reported cause of non-malarial febrile illnesses in Southeast Asia. However, in Malaysia, studies on the prevalence and distribution of rickettsiae have primarily focused on humans, with limited data on these bacteria in vectors and small mammal hosts. Thus, this study aims to investigate the presence of Rickettsia spp. in small mammals and their associated mesostigmatid mites collected from potential rickettsioses areas in Selangor. Animal trapping was conducted across three different ecological study sites comprising a recreational area, agricultural land, and coastal area. A total of 41 small mammals and 363 mesostigmatid mites were collected and identified. Ten percent of the total individual mites were processed for morphological examination, and the remaining mites were then pooled by hosts, with five individual mites per tube, for DNA extraction. The collected samples, comprising blood, animal tissue, and pooled mites, were subjected to DNA extraction and were screened for Rickettsia spp. via nested polymerase chain reaction (PCR), targeting the citrate synthase-encoding gene (gltA) and outer membrane protein B gene (ompB). Interestingly, two pools (3.33%) of Laelaps spp. recovered from Maxomys whiteheadi and Bandicota indica, collected from a recreational area, tested positive for Rickettsia spp. Sequence analysis and phylogenetic tree of the ompB gene revealed the presence of Rickettsia felis in both laelapid mite pools. To our knowledge, this study provides the first molecular detection of R. felis in Laelaps spp. in Malaysia. Full article

This study innovatively presents a hollow-core anti-resonant fiber integrating double-tube nesting and a single-layer anti-resonant wall. Featuring an exclusive two-layer cladding configuration along with an outer cladding circular ring, it differs significantly from traditional fibers. After careful parameter optimization, at 1.55 μm wavelength, the fiber shows excellent performance. Its confinement loss drops to 0.00088 dB/km, 1–2 orders lower than traditional ones. The proportion between the loss of the lowest higher-order mode and that of the fundamental mode reaches 19,900, indicating excellent single-mode performance. In the case of a bending radius of 11–14.2 cm, the x-polarization loss is below 0.001 dB/km, showing good bending resistance. Through structural comparisons, this paper quantitatively reveals the effects of the anti-resonant wall, cladding tube, and outer cladding ring on fiber performance. From the practical fiber-drawing process, it thoroughly analyzes the impact of the outer connecting tube’s offset angle on fiber performance. This research provides crucial theoretical support for new hollow-core fiber design, manufacture, and application, and is expected to drive technological innovation in this field. Full article