Experimental research on creep behaviors of sandstone under uniaxial compressive and tensile stresses

The consideration of time dependence is essential for the study of deformation and fracturing processes of rock materials, especially for those subjected to strong compressive and tensile stresses. In this paper, the self-developed direct tension device and creep testing machine RLW-2000M are used to conduct the creep tests on red sandstone under uniaxial compressive and tensile stresses. The short-term and long-term creep behaviors of rocks under compressive and tensile stresses are investigated, as well as the long-term strength of rocks. It is shown that, under low-stress levels, the creep curve of sandstone consists of decay and steady creep stages; while under high-stress levels, it presents the accelerated creep stage and creep fracture presents characteristics of brittle materials. The relationship between tensile stress and time under uniaxial tension is also put forward. Finally, a nonlinear viscoelastoplastic creep model is used to describe the creep behaviors of rocks under uniaxial compressive and tensile stresses.

Radium-traced nutrient outwelling from the Subei Shoal to the Yellow Sea:Fluxes and environmental implication

The Subei Shoal is the largest sandy ridge in the southern Yellow Sea and is important source for nutrient loading to the sea.Here,the nutrient fluxes in the Subei Shoal associated with eddy diffusion and submarine groundwater discharge(SGD)were assessed to understand their impacts on the nutrient budget in the Yellow Sea.Based on the analysis of 223 Ra and 224 Ra in the field observation,the offshore eddy diffusivity mixing coefficient and SGD were estimated to be 2.3×10^(8)cm^(2)/s and 2.6×10^(9)m^(3)/d(16 cm/d),respectively,in the Subei Shoal.Combined the significant offshore decreasing gradients of nutrient in seawater of the Subei Shoal,the spatially integrated nutrient outwelling fluxes to the Yellow Sea were 262-1465μmol/(m^(2)·d)for DIN,5.2-21μmol/(m^(2)·d)for DIP and711-913μmol/(m^(2)·d)for DSi.Compared to the riverine input,atmospheric deposition and mariculture,nutrient outwelling from the Subei Shoal might play an important role in nutrient budget of the Yellow Sea.These nutrient fluxes could provide 4.1%-23%N and 1.3%-5.3%P requirements for the primary productivity,and the deviated DIN/DIP ratios have the potential to affect the growth of phytoplankton in the marine ecosystem of the Yellow Sea.

Nanoparticle drug delivery system for the treatment of brain tumors:Breaching the blood–brain barrier

To the Editor:Malignant brain tumors represent a substantial morbidity and mortality burden globally,with 308,102 new cases and 251,329 cancer-related deaths in 20201.Brain tumors encompass primary tumors originating in the brain and brain metastases(BM)that have been spread from cancer lesions of other organs.Besides,BM are the most prevalent intracranial malignant tumor affecting approximately 20%e40%of cancer patients2.

Pulmonary rehabilitation restores limb muscle mitochondria and improves the intramuscular metabolic profile

Background: Exercise, as the cornerstone of pulmonary rehabilitation, is recommended to chronic obstructive pulmonary disease (COPD) patients. The underlying molecular basis and metabolic process were not fully elucidated. Methods: Sprague-Dawley rats were classified into five groups: non-COPD/rest ( n = 8), non-COPD/exercise ( n = 7), COPD/rest ( n = 7), COPD/medium exercise ( n = 10), and COPD/intensive exercise ( n = 10). COPD animals were exposed to cigarette smoke and lipopolysaccharide instillation for 90 days, while the non-COPD control animals were exposed to room air. Non-COPD/exercise and COPD/medium exercise animals were trained on a treadmill at a decline of 5° and a speed of 15 m/min while animals in the COPD/intensive exercise group were trained at a decline of 5° and a speed of 18 m/min. After eight weeks of exercise/rest, we used ultrasonography, immunohistochemistry, transmission electron microscopy, oxidative capacity of mitochondria, airflow-assisted desorption electrospray ionization-mass spectrometry imaging (AFADESI-MSI), and transcriptomics analyses to assess rectal femoris (RF). Results: At the end of 90 days, COPD rats’ weight gain was smaller than control by 59.48 ± 15.33 g ( P = 0.0005). The oxidative muscle fibers proportion was lower ( P < 0.0001). At the end of additional eight weeks of exercise/rest, compared to COPD/rest, COPD/medium exercise group showed advantages in weight gain, femoral artery peak flow velocity (Δ58.22 mm/s, 95% CI: 13.85-102.60 mm/s, P = 0.0104), RF diameters (Δ0.16 mm, 95% CI: 0.04-0.28 mm, P = 0.0093), myofibrils diameter (Δ0.06 μm, 95% CI: 0.02-0.10 μm, P = 0.006), oxidative muscle fiber percentage (Δ4.84%, 95% CI: 0.15-9.53%, P = 0.0434), mitochondria oxidative phosphorylate capacity ( P < 0.0001). Biomolecules spatial distribution in situ and bioinformatic analyses of transcriptomics suggested COPD-related alteration in metabolites and gene expression, which can be impacted by exercise. Conclusion: COPD rat model had multi-level structure and function impairment, which can be mitigated by exercise.

珠江河口区大型底栖动物群落结构

河口区大型底栖动物具有的重要群落特征往往可以反映群落所经历的环境污染。为更好地了解珠江河口区大型底栖动物群落结构,作者于2014年11月至2015年8月进行了4个季度的大型底栖动物调查,并利用PRIMER 6.0软件进行群落生物多样性指数计算、群落等级聚类(Cluster)和非度量多维标度排序(nMDS)分析。研究结果显示:珠江河口区共获得大型底栖动物52种,优势种包括光滑河篮蛤(Potamocorbulalaevis)、中国绿螂(Glaucomya chinensis)、焦河篮蛤(Potamocorbulaustulata)和羽须鳃沙蚕(Dendronerispinnaticirrus)。大型底栖动物年平均密度为269.3 ind./m^2,年平均生物量为129.61g/m^2。12个站次的丰富度指数(D)、均匀度指数(J’)和Shannon-Wiener多样性指数(H’)平均值分别为1.81±1.38、0.50±0.27和1.60±1.13。该结果显示除P01断面的秋季和冬季环境质量为优良外,其他站位在不同季度都显示出轻度到重度的污染。Cluster聚类分析和n MDS标序结果表明, P01断面与P02和P03断面群落相似度较低,与断面地理分布情况一致;P02断面和P03断面存在交叉聚集,群落相似度较高。结合环境因子结果可知,沉积物理化因子与群落分布特征相关性较大,其中最能解释珠江河口区群落多样性分布特征的环境因子为盐度和pH值。

Epitaxial growth of large-area and highly crystalline anisotropic ReSe2 atomic layer

The anisotropic two-dimensional （2D） layered material rhenium disulfide （ReSe2） has attracted considerable attention because of its unusual properties and promising applications in electronic and optoelectronic devices. However, because of its low lattice symmetry and interlayer decoupling, anisotropic growth and out-of-plane growth occur easily, yielding thick flakes, dendritic structure, or flower-like structure. In this stud34 we demonstrated a bottom-up method for the controlled and scalable synthesis of ReSe2 by van der Waals epitaxy. To achieve controllable growth, a micro-reactor with a confined reaction space was constructed by stacking two mica substrates in the chemical vapor deposition system. Within the confined reaction space, the nucleation density and growth rate of ReSe2 were significantly reduced, favoring the large-area synthesis of ReSe2 with a uniform monolayer thickness. The morphological evolution of ReSe2 with growth temperature indicated that the anisotropic growth was suppressed at a low growth temperature （〈600 ℃）. Field-effect transistors employing the grown ReSe2 exhibited p-type conduction with a current ON/OFF ratio up to 10s and a hole carrier mobility of 0.98 cm^2/（V·s）. Furthermore, the ReSe2 device exhibited an outstanding photoresponse to near-infrared light, with responsivity up to 8.4 and 5.1 A/W for 850- and 940-nm light, respectively. This work not only promotes the large-scale application of ReSe2 in high-performance electronic devices but also clarifies the growth mechanism of low-lattice symmetry 2D materials.

Doping modulated in-plane anisotropic Raman enhancement on layered or ReS2

Anisotropic two-dimensional (2D) materials exhibit lattice-orientation dependent optical and electrical properties. Carriers doping of such materials has been used to modulate their energy band structures for opto-electronic applications. Herein, we show that by stacking monolayer rhenium disulfide (ReS2) on a flat gold film, the electrons doping in ReS2 can affect the in-plane anisotropic Raman enhancement of molecules adsorbed on ReS2. The change of enhancement factor and the degree of anisotropy in enhancement with layer number are sensitively dependent on the doping level of ReS2 by gold, which is further confirmed by Kelvin probe force microscopy (KPFM) measurements. These findings could open an avenue for probing anisotropic electronic interactions between molecules and 2D materials with low symmetry using Raman enhancement effect.

2009-2018年呼伦贝尔高原蒙古旱獭鼠疫疫源地宿主动物监测结果分析

目的分析蒙古旱獭鼠疫疫源地宿主动物监测情况,为鼠疫防治提供参考依据。方法按"全国鼠疫监测方案"及实施细则进行监测,整理2009-2018年呼伦贝尔市疾病预防控制中心上报的鼠疫监测总结及监测地区在鼠疫防治信息管理系统中上报的数据。采用描述流行病学方法、秩和检验分析鼠密度,P<0.05为差异有统计学意义。结果 2009-2018年捕获啮齿动物2目5科10属11种6 535只,包括达乌尔黄鼠、蒙古旱獭、黑线毛足鼠、五趾跳鼠、长爪沙鼠、黑线仓鼠、布氏田鼠、小家鼠、达乌尔鼠兔、狭颅田鼠、褐家鼠;蒙古旱獭最高密度0. 1 6只/k m 2,最低密度0. 0 2只/k m 2,平均密度0. 0 7只/k m 2,其中陈巴尔虎旗监测的蒙古旱獭数占全部观察或捕获数量的95.80%;达乌尔黄鼠平均密度0.50只/km2,不同地区达乌尔黄鼠的密度差异有统计学意义(χ^2=10.380,P=0.006);鼠体染蚤率29.61%,鼠体蚤指数1.06;从新巴尔虎右旗、满洲里市达乌尔黄鼠检出鼠疫阳性血清11份,最高滴度为1∶1 280。结论呼伦贝尔地区蒙古旱獭总体密度一直保持较低水平;达乌尔黄鼠成为优势种并携带较高滴度的鼠疫抗体,提示存在动物鼠疫的流行,应加强动物和人间鼠疫的监测和防控。

Research on the influence of contact surface constraint on mechanical properties of rock-concrete composite specimens under compressive loads

The contact form of rock-concrete has a crucial influence on the failure characteristics of the stability of rock-concrete engineering.To study the influence of contact surface on the mechanical properties of rock-concrete composite specimens under compressive loads,the two different contact forms of rock-concrete composite specimens are designed,the mechanical properties of these two different specimens are analyzed under triaxial compressive condition,and analysis comparison on the stress-strain curves and failure forms of the two specimens is carried out.The influence of contact surface constraint on the mechanical properties of rock-concrete composite specimens is obtained.Results show that the stress and strain of rock-concrete composite specimens with contact surface constraint are obviously higher than those without.Averagely,compared with composite specimens without the contact surface,the existence of contact surface constraint can increase the axial peak stress of composite specimens by 24%and the axial peak strain by 16%.According to the characteristics of the fracture surface,the theory of microcrack development is used to explain the contact surface constraint of rock-concrete composite specimens,which explains the difference of mechanical properties between the two rock-concrete composite specimens in the experiment.Research results cannot only enrich the research content of the mechanics of rock contact,but also can serve as a valuable reference for the understanding of the corresponding mechanics mechanism of other similar composite specimens.