Experimental study on the acoustic roughness spectrum of high-speed railway rails

Purpose–This study aims to investigate the acoustic roughness of rails on China’s high-speed railways,with a focus on short-wavelength irregularities(less than 80 cm),which are known to significantly contribute to noise.The goal is to develop a specific acoustic roughness spectrum tailored for China’s high-speed railway system,as no such spectrum currently exists.Design/methodology/approach–A long-term tracking study was conducted on major railway lines in China,monitoring rail roughness throughout the initial operational period and the rails’service life.Data preprocessing techniques such as peak removal and curvature correction were applied for acoustic adjustments.A spatial-wavelength domain transformation was performed,providing the distribution patterns and statistical characteristics of acoustic roughness on China’s high-speed rails.Based on these analyses,a model for constructing the acoustic roughness spectrum was developed.Findings–The study found that the acoustic roughness of China’s high-speed railway rails follows aχ2 distribution with six degrees of freedom.For wavelengths greater than 8 cm,the acoustic roughness spectrum remains below the ISO specified limits.In the wavelength range of 3.2 cm to 6.3 cm,the roughness is comparable to or within the limits specified by ISO 3095:2005 and ISO 3095:2013.However,for wavelengths shorter than 2.5 cm,the roughness exceeds ISO limits.Originality/value–This research fills the gap in the lack of a specific acoustic roughness spectrum for China’s high-speed railways.By establishing a tailored spectrum based on long-term data analysis,the findings provide valuable insights for noise control and rail maintenance in the context of China’s high-speed rail system.

Ultrasensitive detection of endocrine disruptors via superfine plasmonic spectral combs

The apparent increase in hormone-induced cancers and disorders of the reproductive tract has led to a growing demand for new technologies capable of detecting endocrine disruptors.However,a long-lasting challenge unaddressed is how to achieve ultrahigh sensitive,continuous,and in situ measurement with a portable device for infield and remote environmental monitoring.Here we demonstrate a simple-to-implement plasmonic optical fiber biosensing platform to achieve an improved light–matter interaction and advanced surface chemistry for ultrasensitive detection of endocrine disruptors.Our platform is based on a gold-coated highly tilted fiber Bragg grating that excites high-density narrow cladding mode spectral combs that overlap with the broad absorption of the surface plasmon for high accuracy interrogation,hence enabling the ultrasensitive monitoring of refractive index changes at the fiber surface.Through the use of estrogen receptors as the model,we design an estradiol–streptavidin conjugate with the assistance of molecular dynamics,converting the specific recognition of environmental estrogens(EEs)by estrogen receptor into surface-based affinity bioassay for protein.The ultrasensitive platform with conjugate-induced amplification biosensing approach enables the subsequent detection for EEs down to 1.5×10−3 ng ml−1 estradiol equivalent concentration level,which is one order lower than the defined maximal E2 level in drinking water set by the Japanese government.The capability to detect EEs down to nanogram per liter level is the lowest limit of detection for any estrogen receptor-based detection reported thus far.Its compact size,flexible shape,and remote operation capability open the way for detecting other endocrine disruptors with ultrahigh sensitivity and in various hard-toreach spaces,thereby having the potential to revolutionize environment and health monitoring.

Acute toxicity assessment of drinking water source with luminescent bacteria: Impact of environmental conditions and a case study in Luoma Lake, East China

Protecting the quality of lake watersheds by preventing and reducing their contamination is an effective approach to ensure the sustainability of the drinking water supply.In this study,acute toxicity assessment was conducted on the basis of acute bioluminescence inhibition assay using the marine bacterium Vibrio fischeri as the test organism and Luoma Lake drinking water source in East China as the research target.The suitable ranges of environmental factors,including pH value,organic matter,turbidity,hardness,and dissolved oxygen of water samples were evaluated for the toxicity testing of bioluminescent bacteria.The physicochemical characteristics of water samples at the selected 43 sites of Luoma Lake watershed were measured.Results showed that the variations in pH value(7.31-8.41),hardness(5-20°d)and dissolved oxygen(4.44-11.03 mg/L)of Luoma Lake and its main inflow and outflow rivers had negligible impacts on the acute toxicity testing of V.fischeri.The luminescence inhibition rates ranged from-11.21%to 10.80%at the 43 sites.Pearson's correlation analysis in the experiment revealed that temperature,pH value,hardness,and turbidity had no correlation with luminescence inhibition rate,whereas dissolved oxygen showed a weak statistically positive correlation with a Pearson correlation coefficient of 0.455(p<0.05).

Label-free colorimetric nanosensor with improved sensitivity for Pb^2+ in water by using a truncated 8-17 DNAzyme

Water pollution accidents, such as the Flint water crisis in the United States, caused by lead contamination have raised concern on the safety of drinking water distribution systems. Thus, the routine monitoring of lead in water is highly required and demands efficient, sensitive, cost-effective, and reliable lead detection methods. This study reports a label-free colorimetric nanosensor that uses unmodified gold nanoparticles (AuNPs) as indicators to enable rapid and ultra-sensitive detection of lead in environmental water. The 8-17 DNAzyme was truncated in this study to facilitate the detachment of single-stranded DNA fragments after substrate cleavage in the presence of Pb「. The detached fragments were adsorbed over AuNPs and protected against salt concentration-induced aggregation. Accordingly, high Pb^2+ would result in rapid color change from blue to pink. The established sensing principle achieved a sensitive limit of detection of 0.2×10^-9mol/L Pb^2+. with a linear working range of two orders of magnitude from 0.5×10^-9mol/L to 5×10^-9mol/L. The selectivity of the nanosensor was demonstrated by evaluating the interfering metal ions. The developed nanosensor can serve as a substitute for the rapid analysis and monitoring of trace lead levels under the drinking water distribution system and even other environmental water samples.