262 research outputs found
Tuning Co valence state in cobalt oxyhydrate superconductor by post reduction
We report a successful tuning of Co valence state in cobalt oxyhydrate
superconductor via a facile post reduction using NaOH as reducing agent. The
change in Co valence was precisely determined by measuring the volume of the
released oxygen. The possible hydronium-incorporation was greatly suppressed in
concentrated NaOH solution, making the absolute Co valence determinable. As a
result, an updated superconducting phase diagram was obtained, which shows that
the superconducting transition temperature increases monotonically with
increasing Co valence in a narrow range from +3.58 to +3.65.Comment: 17 pages, 5 figures and 1 table. Chem. Mat. in pres
First order transition in PbCu(PO)O () containing CuS
Lee et al. reported that the compound LK99, with a chemical formula of
PbCu(PO)O (), exhibits room-temperature
superconductivity under ambient pressure. In this study, we investigated the
transport and magnetic properties of pure CuS and LK-99 containing CuS.
We observed a sharp superconducting-like transition and a thermal hysteresis
behavior in the resistivity and magnetic susceptibility. However, we did not
observe zero-resistivity below the transition temperature. We argue that the
so-called superconducting behavior in LK-99 is most likely due to a reduction
in resistivity caused by the first order structural phase transition of CuS
at around 385 K, from the phase at high temperature to the
phase at low temperature
Study on the Creep Characteristics of Sandstone under Coupled Stress-water Pressure
Long-term interaction between stress and water pressure leads to creep damage of reservoir bank slope. As a result there will be instability of the bank slopes in many water conservancy projects. The rock mass creeping effect of coupled stress-water pressure was studied by using a typical sandstone rock from the Three Gorges reservoir area. The experiment was conducted by using the rock immersion-air-drying cyclic load rheometer device (designed and manufactured by our research team). Based on the experimental results, the following key points were observed: 1) the creep strain and the steady-state creep rate was increasing when the water pressure increased (at the same stress level). Under the same water pressure, the increase in the axial pressure resulted in the increase in the creep strain and steady creep rate of the sandstone specimens. 2) the increase in the axial pressure increased the creep strain and steady-state creep rate of the sandstone specimens while the water pressure increased. The mechanical properties of the sandstone specimens were affected by the water pressure. 3) the water infiltrates through the pore surfaces. As a result, the rate of deformation will increase while the bearing capacity and long-term strength of the rock decrease. This paper provides a solid theoretical foundation for the evaluation and prediction of reservoir geological hazards
Alteration of cystic airway mesenchyme in congenital pulmonary airway malformation.
Congenital pulmonary airway malformation (CPAM) is the most common congenital lesion detected in the neonatal lung, which may lead to respiratory distress, infection, and pneumothorax. CPAM is thought to result from abnormal branching morphogenesis during fetal lung development, arising from different locations within the developing respiratory tract. However, the pathogenic mechanisms are unknown, and previous studies have focused on abnormalities in airway epithelial cells. We have analyzed 13 excised lung specimens from infants (age <ā1 year) with a confirmed diagnosis of type 2 CPAM, which is supposed to be derived from abnormal growth of intrapulmonary distal airways. By examining the mesenchymal components including smooth muscle cells, laminin, and elastin in airway and cystic walls using immunofluorescence staining, we found that the thickness and area of the smooth muscle layer underlining the airway cysts in these CPAM tissue sections were significantly decreased compared with those in bronchiolar walls of normal controls. Extracellular elastin fibers were also visually reduced or absent in airway cystic walls. In particular, a layer of elastin fibers seen in normal lung between airway epithelia and underlying smooth muscle cells was missing in type 2 CPAM samples. Thus, our data demonstrate for the first time that airway cystic lesions in type 2 CPAM occur not only in airway epithelial cells, but also in adjacent mesenchymal tissues, including airway smooth muscle cells and their extracellular protein products. This provides a new direction to study the molecular and cellular mechanisms of CPAM pathogenesis in human
Retraction notice to āPeriodic Solutions of Second Order Impulsive Differential Equations at Resonance via Variational Approachā [Math. Model. Anal. 19(5):664ā675, 2014]
The following article is being retracted from publication in Mathematical Modelling and Analysis Journal:
Periodic Solutions of Second Order Impulsive Diļ¬erential Equations at Resonance via Variational Approach, by
Jin Li, Jianlin Luo and Zaihong Wang,
Volume 19, Issue 5, 2014, pp. 664ā675,
Mathematical Modelling and Analysis, DOI: 10.3846/13926292.2014.980864
http://www.tandfonline.com/doi/abs/10.3846/13926292.2014.980864
Received 10 February 2014, published online 24 November 2014,
since the same results are published in Springer article
Andesman-Lazer type condition for second-order diļ¬erential equations at resonance with impulsive eļ¬ects, by
Jin Li and Meilin Zheng,
Advances in Diļ¬erence Equations, DOI: 10.1186/1687-1847-2014-235
http://www.advancesindiļ¬erenceequations.com/content/2014/1/235
Received 10 June 2014, published 9 September 2014.
The Editors and publishers of the journal, Taylor & Francis, note that we received, peer-reviewed, accepted and published the article on the basis that the authors are presenting original results and are not intending to publish them in any other journal.
The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as āretractedā
Study on the Time-lag Failure of Sandstone With Different Degrees of Unloading Damage
The unloading effect of rock mass excavation is an inevitable practice, and itās often characterized by a relatively large-scale engineering hazard with a noticeable time lag.A set of unloading triaxial tests were conducted on a sandstone rock to establish the deformation law and the threshold time. Based on the renormalization group theory, the unloading sandstone model was developed by considering the interaction between particles. Similarly, a logistic model was used to predict the unloading damage of sandstone. The unloading time lag damage of sandstone rock was predicted by using the damage threshold. The research shows that: (1) The higher the degree of unloading, the shorter the time-lag failure. (2) The damage range of critical values was optimized. (3) The error between the predicted value and the experimental value of the time threshold was almost less than 5 %, the prediction result was found to be good, and the employed logistic evolution model was reasonable. The findings of this research provide a prediction method and precise information about the mechanism of unloading time lag deformation. Therefore, it can be used as a reference for excavation-support design of underground structures
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