Investigating characteristics of the long-term settlement of railway embankments in warm permafrost areas

Introduction: The embankment in the permafrost zone of the Qinghai–Tibet Railway (QTR) faces the problem of permafrost degradation, especially in the warm and ice-rich permafrost areas. The settlement deformation of the embankment is more serious in these areas.Methods: This study systematically investigates the settlement deformation characteristics during 16 operational years of three types of typical roadbed structures. The traditional embankment (TE), U-shaped crushed-rock embankment (UCRE), and crushed-rock revetment embankment (CRRE) are the roadbed structures. The long-term monitoring ground temperature and deformation data of the embankment section along the QTR in warm permafrost areas from 2005 to 2020 are utilized in analysis.Results and Discussion: This study focuses on the influence law of the roadbed structure form, shady–sunny slope effect, and temperature field change on the settlement of the roadbed. The results indicated that the two types of the crushed-rock embankment (CRE) of the long-term cumulative settlement are less than 50% of the cumulative settlement of the TE, and the impact on controlling the settlement is significant. The annual settlements of the three types of embankment structures are related to the artificial permafrost table (APT) and influenced by cyclical climate change at the regional scale. The annual growth rate of the settlement at the left and right shoulders of the UCRE as a result of the effect of the shady–sunny slope does not vary considerably as the number of operational years increases. The impact of the shady–sunny slope on the CRRE for the various settlements before 2008 was negligible. After 2008, the thermal disturbance to the embankment temperature field induced by the preconstruction and the effect of shady–sunny slopes decreased gradually as the number of operational years increased. In some years of operation, a thawed interlayer in the TE and CRRE greatly affected the embankment settlement acceleration. The settlement growth rate of the TE is related to the decline of the artificial permafrost table (APT). During the operational years, there was no thawed interlayer in the UCRE. The development of the settlement rate is unaffected by the temperature field for either the left or right embankment shoulder

The positivity rates and drug resistance patterns of Mycobacterium tuberculosis using nucleotide MALDI-TOF MS assay among suspected tuberculosis patients in Shandong, China: a multi-center prospective study

ObjectiveTo investigate the positivity rates and drug resistance characteristics of Mycobacterium tuberculosis (MTB) among suspected tuberculosis (TB) patients in Shandong Province, the second-largest population province in China.MethodsA prospective, multi-center study was conducted from April 2022 to June 2023. Pathogen and drug resistance were identified using nucleotide matrix-assisted laser desorption ionization time-of-flight mass spectrometry (nucleotide MALDI-TOF MS).ResultsOf 940 suspected TB patients included in this study, 552 cases were found to be infected with MTB giving an overall positivity rate of 58.72%. Total of 346 cases were resistant to arbitrary anti-TB drug (62.68%), with Zibo (76.47%), Liaocheng and Weihai (both 69.23%) ranking top three and TB treatment history might be a related factor. Monoresistance was the most common pattern (33.53%), with isoniazid the highest at 12.43%, followed by rifampicin at 9.54%. Further analysis of gene mutations conferring resistance revealed diverse types with high heteroresistance rate found in multiple anti-TB drugs.ConclusionA relatively high rate of MTB positivity and drug resistance was found in Shandong Province during and after the COVID-19 pandemic, indicating the need for strengthening rapid identification of species and drug resistance among suspected TB patients to guide better medication and minimize the occurrence of drug resistance

A new bound on the block restricted isometry constant in compressed sensing

Abstract This paper focuses on the sufficient condition of block sparse recovery with the l 2 / l 1 $l_{2}/l_{1}$ -minimization. We show that if the measurement matrix satisfies the block restricted isometry property with δ 2 s | I < 0.6246 $\delta_{2s|\mathcal{I}}< 0.6246$ , then every block s-sparse signal can be exactly recovered via the l 2 / l 1 $l_{2}/l_{1}$ -minimization approach in the noiseless case and is stably recovered in the noisy measurement case. The result improves the bound on the block restricted isometry constant δ 2 s | I $\delta_{2s|\mathcal {I}}$ of Lin and Li (Acta Math. Sin. Engl. Ser. 29(7):1401-1412, 2013)

Copper fertilizer effects on copper distribution and vertical transport in soils

The fate of Cu fertilizer in soils is important for its plant availability and environmental significance. Little research has been done to investigate the status of Cu in soil under repeated application of Cu fertilizer. A field study was conducted to determine the distribution and transport of Cu in soil profiles after 17 years' applications of Cu fertilizer. Soil samples obtained at different application times and soil depths were analyzed for labile Cu by a diethylenetriaminepentaacetic acid (DTPA) extraction procedure. A modified sequential extraction technique was used to separate soil Cu into exchangeable (Exe), organic matter weakly bound (Wbo), carbonate bound (Carb), manganese oxides bound (MnOx), organic matter specifically bound (Sbo), and mineral bound (Min) fractions. The results showed that long-term application of Cu fertilizer caused the accumulation of Cu in the surface soil. The accumulation of soil Cu in the 0-15 cm and 0-60 cm soil layers accounted for 41.3% and 57.3% of the Cu applied over 17 years. Calculations indicated that little Cu was removed from the plots by crop harvest, which meant that about 40% of fertilizer Cu leached below the 60 cm soil depth. Additional evidence suggested that some Cu leached below 400 cm. Total labile Cu and the increase in labile Cu in the surface layer soil followed a linear relationship with the amount of Cu added and with the application time of the Cu fertilizer. Copper bound to minerals and weakly bound to organic matter accounted for 76% to 92% of the total Cu in soil. In addition, the two fractions had the same distribution trend in the soil profile. The Cu content of different fractions declined in a similar order, i.e. Min-Cu &gt; WboCu &gt; Exe-Cu &gt; Sbo-Cu &gt; Carb-Cu &gt; MnOx-Cu, regardless of Cu treatment. Most Cu added to soil entered into Min, Exe, Who, and Carb fractions. The Exe-Cu, Wbo-Cu, and Carb-Cu fractions are readily mobile and can be used to predict Cu transport. The transport ability of Cu fractions followed the order of Wbo-Cu &gt; Exe-Cu &gt; Carb-Cu and increased with increasing soil depth. These results indicate that the accumulation of Cu in the soil resulting from the long-term application of Cu fertilizer could pose an environmental risk due to the downward mobility of Cu. (c) 2006 Elsevier B.V. All rights reserved

Quadruple-band metamaterial absorber based on the cuboid dielectric particles

In this work, a quadruple-band dielectric metamaterial absorber (MMA) was proposed and studied, which is composed of eight cuboid dielectric particles and a metallic ground plate. When electromagnetic wave is incident on the dielectric particles, dielectric particles act as resonators and produce abundant resonant modes, which can result in perfect absorption. In simulation, four absorption peaks are observed at 9.13, 9.62, 10.0 and 10.46GHz with 88%, 89%, 100% and 96%, respectively. By adjusting geometry parameters of the dielectric particles, dielectric MMAs with different bands can be obtained. Further investigation shows that the absorption peaks can be changed by increasing the permittivity of the dielectric. Based on the designing technique of using simple cuboid dielectric particles directly acting as resonator, this work provides a simple method to construct multiband all-dielectric MMA