An Experimental Evaluation of the Weathering Effects on Mine Shaft Lining Materials

Many shaft collapses are related to the deterioration and failure of the masonry shaft lining materials. In modern mine shaft, concrete is widely used to provide support. To analyse shafts stability, the properties of the lining need to be well defined. The behaviour of masonry and concrete can be considerably affected by long-term exposure to harsh mine water. This paper presents a study which focuses on the weathering effects of mine water on lining materials (brick, mortar, and concrete). To reproduce the weathering process, samples were placed into solutions of potable water, artificial mine water, and a more aggressive mine-water solution for just less than one year. Four phases of laboratory tests were conducted throughout the time period to assess the degradation of mechanical properties of the lining materials. Particular attention is given to the degradation of material strength and stiffness. Results indicate that the harsh acidic mine water has pronounced detrimental effects on the strength and stiffness of mortar. The weathering process is shown to have the most significant effect on the stiffness of concrete and mortar. It is also shown that the use of mass loss as an index for evaluation of mechanical properties may not be appropriate

Th gme 10: A numerical model to capture the geotechnical response to coal combustion at an underground coal gasification site

A detailed numerical modelling study was carried out to represent geotechnical aspects of the Wieczorek underground coal gasification (UCG) site in Poland. A coupled thermos-mechanical numerical model was created to represent a single coal burning panel. The coal burning proceb was simulated by modifying the energy balance equation with an additional term related to the calorific value of coal as a source. Temperature dependent material properties were abigned to the coupled thermal-mechanical model according to published data. In the model, the burning zone spread about 7.5m laterally after 20 days of burning. Results from the coupled model were used to gauge a worst-case scenario in terms of the potential size of a formed cavity. This data was used within a leb computationally expensive mechanicalonly numerical model in order to evaluate the ground subsidence caused by the worst-case scenario for single and multiple UCG burning panels. The single panel burning resulted in 23mm of ground subsidence at the top of the model after long term coal burning. The ground subsidence measured at the top of the model, at the center point of the gasification arrangement, was approximately 72mm when five panels were burnt with an edge to edge panel distance of 5m; this was increased to 85mm for seven panels. The numerical modelling results have implications to the industrial application of UCG

Macrophage phenotypic subtypes diametrically regulate epithelial-mesenchymal plasticity in breast cancer cells

Background: Metastatic progression of breast cancer involves phenotypic plasticity of the carcinoma cells moving between epithelial and mesenchymal behaviors. During metastatic seeding and dormancy, even highly aggressive carcinoma cells take on an E-cadherin-positive epithelial phenotype that is absent from the emergent, lethal metastatic outgrowths. These phenotypes are linked to the metastatic microenvironment, though the specific cells and induction signals are still to be deciphered. Recent evidence suggests that macrophages impact tumor progression, and may alter the balance between cancer cell EMT and MErT in the metastatic microenvironment. Methods: Here we explore the role of M1/M2 macrophages in epithelial-mesenchymal plasticity of breast cancer cells by coculturing epithelial and mesenchymal cells lines with macrophages. Results: We found that after polarizing the THP-1 human monocyte cell line, the M1 and M2-types were stable and maintained when co-cultured with breast cancer cells. Surprisingly, M2 macrophages may conferred a growth advantage to the epithelial MCF-7 cells, with these cells being driven to a partial mesenchymal phenotypic as indicated by spindle morphology. Notably, E-cadherin protein expression is significantly decreased in MCF-7 cells co-cultured with M2 macrophages. M0 and M1 macrophages had no effect on the MCF-7 epithelial phenotype. However, the M1 macrophages impacted the highly aggressive mesenchymal-like MDA-MB-231 breast cancer cells to take on a quiescent, epithelial phenotype with re-expression of E-cadherin. The M2 macrophages if anything exacerbated the mesenchymal phenotype of the MDA-MB-231 cells. Conclusion: Our findings demonstrate M2 macrophages might impart outgrowth and M1 macrophages may contribute to dormancy behaviors in metastatic breast cancer cells. Thus EMT and MErT are regulated by selected macrophage phenotype in the liver metastatic microenvironment. These results indicate macrophage could be a potential therapeutic target for limiting death due to malignant metastases in breast cancer

Pulmonary vasoconstrictor action of KCNQ potassium channel blockers

KCNQ channels have been widely studied in the nervous system, heart and inner ear, where they have important physiological functions. Recent reports indicate that KCNQ channels may also be expressed in portal vein where they are suggested to influence spontaneous contractile activity. The biophysical properties of K+ currents mediated by KCNQ channels resemble a current underlying the resting K+ conductance and resting potential of pulmonary artery smooth muscle cells. We therefore investigated a possible role of KCNQ channels in regulating the function of pulmonary arteries by determining the ability of the selective KCNQ channel blockers, linopirdine and XE991, to promote pulmonary vasoconstriction. Linopirdine and XE991 both contracted rat and mouse pulmonary arteries but had little effect on mesenteric arteries. In each case the maximum contraction was almost as large as the response to 50 mM K+. Linopirdine had an EC50 of around 1 μM and XE991 was almost 10-fold more potent. Neither removal of the endothelium nor exposure to phentolamine or α,β-methylene ATP, to block α1-adrenoceptors or P2X receptors, respectively, affected the contraction. Contraction was abolished in Ca2+-free solution and in the presence of 1 μM nifedipine or 10 μM levcromakalim

Using Context-Based Password Strength Meter to Nudge Users' Password Generating Behavior: A Randomized Experiment

Encouraging users to create stronger passwords is one of the key issues in password-based authentication. It is particularly important as prior works have highlighted that most passwords are weak. Yet, passwords are still the most commonly used authentication method. This paper seeks to mitigate the issue of weak passwords by proposing a context-based password strength meter. We conduct a randomized experiment on Amazon MTurk and observe the change in users’ behavior. The results show that our proposed method is significantly effective. Users exposed to our password strength meter are more likely to change their passwords after seeing the warning message, and those new passwords are stronger. Furthermore, users are willing to invest their time to learn about creating a stronger password, even in a traditional password strength meter setting. Our findings suggest that simply incorporating contextual information to password strength meters could be an effective method in promoting more secure behaviors among end users

Cell number quantification of USPIO-labeled stem cells by MRI: An in vitro study

MRI plays an expanding role in stem cell therapies. The non-invasive nature and high spatial resolution of MR imaging make MR imaging a powerful tool to investigate biologic processes at the molecular and cellular level in vivo longitudinally. Quantitative detection of stem cells after transplantation may allow assessment of stem cell localization and migration, and monitoring of the therapeutic effectiveness of stem cell therapy. In this study, we present a technique for MR quantification of magnetically labeled mouse embryonic stem cells distributed or injected in agarose gel phantoms. Apparent transverse relaxation rate enhancements (ΔR2*) were measured by gradient echo sequences. The linear relationship between ΔR2* and the concentration of USPIO-labeled mouse embryonic stem cells was observed and used for quantifying cell density and cell number after injection or transplantation. The MRI acquisition and analysis protocol were validated by good agreement between actual cell numbers and MRI-estimated cell numbers over a wide range of cell numbers. This MR technique for cell number and cell density quantification is applicable to future in vivo studies. © 2006 IEEE.published_or_final_versio

Centrifuge Modelling of the Collapse of Shaft Linings

The collapse of abandoned and often hidden mine shafts is a serious problem in the UK and many parts of Europe. The collapse of these shafts is often related to the failure of the shaft lining. Understanding the mechanisms of ground movements around deforming/collapsing mine shafts is, therefore, important in the assessment of mine shaft location as well as lining condition. This paper presents an experimental study of the mechanisms of soil failure around a deforming shaft lining. Geotechnical centrifuge modelling of reduced-scale buried mine shafts was tested to determine the magnitude and pattern of ground deformations that occurred during loss of internal support pressure. An axis-symmetric centrifuge container was used along with half-cylindrical model shafts. These allowed for the acquisition of digital images of the sub-surface soil and mine shafts which enabled the measurement of soil and shaft deformation using image analysis techniques. The results from two model shaft tests are presented. The first test involved the loss of internal support along the entire shaft length, whereas the second test studied the effect of a discrete weakened zone within the lining

The Meaning of Memory Safety

We give a rigorous characterization of what it means for a programming language to be memory safe, capturing the intuition that memory safety supports local reasoning about state. We formalize this principle in two ways. First, we show how a small memory-safe language validates a noninterference property: a program can neither affect nor be affected by unreachable parts of the state. Second, we extend separation logic, a proof system for heap-manipulating programs, with a memory-safe variant of its frame rule. The new rule is stronger because it applies even when parts of the program are buggy or malicious, but also weaker because it demands a stricter form of separation between parts of the program state. We also consider a number of pragmatically motivated variations on memory safety and the reasoning principles they support. As an application of our characterization, we evaluate the security of a previously proposed dynamic monitor for memory safety of heap-allocated data.Comment: POST'18 final versio

Hepatic fibrogenesis requires sympathetic neurotransmitters

Background and aims: Hepatic stellate cells (HSC) are activated by liver injury to become proliferative fibrogenic myofibroblasts. This process may be regulated by the sympathetic nervous system (SNS) but the mechanisms involved are unclear. Methods: We studied cultured HSC and intact mice with liver injury to test the hypothesis that HSC respond to and produce SNS neurotransmitters to promote fibrogenesis. Results: HSC expressed adrenoceptors, catecholamine biosynthetic enzymes, released norepinephrine (NE), and were growth inhibited by α- and β-adrenoceptor antagonists. HSC from dopamine β-hydroxylase deficient (Dbh(−/−)) mice, which cannot make NE, grew poorly in culture and were rescued by NE. Inhibitor studies demonstrated that this effect was mediated via G protein coupled adrenoceptors, mitogen activated kinases, and phosphatidylinositol 3-kinase. Injury related fibrogenic responses were inhibited in Dbh(−/−) mice, as evidenced by reduced hepatic accumulation of α-smooth muscle actin(+ve) HSC and decreased induction of transforming growth factor β1 (TGF-β1) and collagen. Treatment with isoprenaline rescued HSC activation. HSC were also reduced in leptin deficient ob/ob mice which have reduced NE levels and are resistant to hepatic fibrosis. Treating ob/ob mice with NE induced HSC proliferation, upregulated hepatic TGF-β1 and collagen, and increased liver fibrosis. Conclusions: HSC are hepatic neuroglia that produce and respond to SNS neurotransmitters to promote hepatic fibrosis