Finite element method applied in mine pressure computation within the context of rock massif – support system interaction

Purpose. The analysis of the current underground mine workings, both those that are in operation and works located within the mining perimeters where activity was stopped, is leading directly to the problem of stability, i.e. safety. The aim of the paper is the stability analysis of underground workings located in strongly metamorphosed andesite and determination of mine pressure in the context of rock – support system interaction was made based on numerical methods, taking into account the effects of inhomogeneous stresses, anisotropy of rocks, and time. Methods. Numerical – based finite element method was applied to obtain the stress variation radial displacement and mine pressure epures for the analyzed mine workings. To assess the stability of underground mine workings, a mathematical model was developed based on the principle of proper conformity and safety level, according to the main factors that influence the stability of underground workings. Findings. The results obtained showed that underground workings analyzed are characterized by a low stability level, which is consistent with the results obtained by the observations and numerical method. Depending on the computed level of safety has been established correspondence to class stability of underground mine workings. The results are confirmed by in situ observations and solutions obtained by experiments. Originality. The patterns of the stress-strain state change in the context of rock – support system interaction for horizontal galleries located in strongly metamorphosed andesite. Practical implications. The research results will facilitate to improve stability of mine workings and to significantly increase the safety level throughout their entire life – cycle.Мета. Аналіз стійкості підземних гірничих виробок, пройдених у сильно метаморфізованому андезиті, за допомогою чисельних методів моделювання. Визначити характер впливу гірського тиску з урахуванням взаємодії у системі “породний масив – кріплення”, впливу неоднорідних напружень, анізотропії порід і часу. Методика. Чисельний метод кінцевих елементів використовувався для розрахунку радіального зміщення різних напружень і побудови епюри напружень для аналізованої шахти. У якості критерія міцності прийнята гіпотеза Кулона-Мора, узагальнена Друкером-Прагером відповідно до припущень Рейеса. Стійкість підземних виробок оцінювалася за допомогою математичної моделі, яка була створена на основі принципу необхідного рівня конформності та безпеки, відповідно до основних факторів, що впливають на стійкість підземних виробок. Результати. Результати, отримані у ході спостережень і чисельними методами, свідчать про низький рівень стійкості аналізованих підземних виробок. Встановлено, що зі збільшенням поперечного перерізу виробки і глибини її залягання радіальні напруження зростають від контуру до масиву, досягаючи більш низьких значень у порівнянні з напруженим станом в масиві, чим і пояснюється погіршення стійкості виробок. Визначено фактори, за якими оцінена стійкість виробки: рівень відповідності (NC), рівень безпеки (NS) і ступінь невідповідності (GC) на основі отриманої оцінки (PO) та максимальної оцінки (PM). Рекомендовано використовувати у сильно метаморфізованому андезитовому типі порід не жорстке бетонне кріплення, а кріплення з вантажонесучою здатністю, що поступово збільшується. Наукова новизна. Розкрито механізм деформування системи “масив – кріплення” у сильно метаморфізованих андезитових породах. На основі нового математичного підходу до оцінки стійкості виробок встановлено відповідність між критерієм безпеки NS і класом стійкості гірничих виробок. Практична значимість. Результати дослідження сприятимуть поліпшенню стійкості гірничих виробок і значно підвищать рівень виробничої безпеки протягом всього періоду їх експлуатації.Цель. Анализ устойчивости подземных горных выработок, пройденных в сильно метаморфизованном андезите, с помощью численных методов моделирования. Определить характер влияния горного давления с учетом взаимодействия в системе “породный массив – крепь”, влияния неоднородных напряжений, анизотропии пород и времени. Методика. Численный метод конечных элементов использовался для расчета радиального смещения различных напряжений и построения эпюры напряжений для анализируемой шахты. В качестве критерия прочности принята гипотеза Кулона-Мора, обобщенная Друкером-Прагером в соответствии с предположениями Рейеса. Устойчивость подземных выработок оценивалась при помощи математической модели, которая была создана на основе принципа необходимого уровня конформности и безопасности, в соответствии с основными факторами, влияющими на устойчивость подземных выработок. Результаты. Результаты, полученные в ходе наблюдений и численными методами, свидетельствуют о низком уровне устойчивости анализируемых подземных выработок. Установлено, что с увеличением поперечного сечения выработки и глубины ее заложения радиальные напряжения возрастают от контура к массиву, достигая более низких значений по сравнению с напряженным состоянием в массиве, чем и объясняется ухудшение устойчивости выработок. Определены факторы, по которым оценена устойчивость выработки: уровень соответствия (NC), уровень безопасности (NS) и степень несоответствия (GC) на основе полученной оценки (PO) и максимальной оценки (PM). Рекомендовано использовать в сильно метаморфизованном андезитовом типе пород не жесткую бетонную крепь, а крепь с постепенно увеличивающейся грузонесущей способностью. Научная новизна. Раскрыт механизм деформирования системы “массив – крепь” в сильно метаморфизированных андезитовых породах. На основе нового математического подхода к оценке устойчивости выработок установлено соответствие между критерием безопасности NS и классом устойчивости горных выработок. Практическая значимость. Результаты исследования будут способствовать улучшению устойчивости горных выработок и значительно повысят уровень производственной безопасности в течение всего периода их эксплуатации.This work was developed from a theoretical and experimental study on the stability analysis of underground workings located in strongly metamorphosed andesite and determination of mine pressure in the context of rock – support system interaction. We thank to our colleague dr. Gabriel Băbuţ for his assistance and support in developing the mathematical model based on the principle of proper conformity and safety level, according to the main factors that influence the stability of underground workings. We would also like to show our gratitude to the University of Petrosani which provided the necessary equipment to perform all laboratory tests in prior experimental researches leading to the results synthesized in this article

A subaqueous hazard map for earthquake-triggered landslides in Lake Zurich, Switzerland

The awareness of geohazards in the subaqueous environment has steadily increased in the past years and there is an increased need to assess these hazards in a quantitative sense. Prime examples are subaqueous landslides, which can be triggered by a number of processes including earthquakes or human activities, and which may impact offshore and onshore infrastructure and communities. In the literature, a plenitude of subaqueous landslide events are related to historical earthquakes, including cases from lakes in Switzerland. Here, we present an approach for a basin-wide earthquake-triggered subaquatic landslide hazard assessment for Lake Zurich, which is surrounded by a densely populated shoreline. Our analysis is based on high-resolution sediment-mechanical and geophysical input data. Slope stabilities are calculated with a grid-based limit equilibrium model on an infinite slope, which uses Monte Carlo sampled input data from a sediment- mechanical stratigraphy of the lateral slopes. Combined with probabilistic ground-shaking forecasts from a recent national seismic hazard analysis, subaquatic earthquake-triggered landslide hazard maps are constructed for different mean return periods, ranging from 475 to 9975 years. Our results provide a first quantitative landslide hazard estimation for the lateral slopes in Lake Zurich. Furthermore, a back-analysis of a case-study site indicates that pseudostatic accelerations in the range between 0.04 and 0.08 g were needed to trigger a well-investigated subaqueous landslide, dated to *2210 cal. years B.P

Chronic ulcerative stomatitis: Case series of an under‐recognized entity

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146622/1/cup13347_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146622/2/cup13347.pd

Calcium regulates the PI3K-Akt pathway in stretched osteoblasts

AbstractMechanical loading plays a vital role in maintaining bone architecture. The process by which osteoblasts convert mechanical signals into biochemical responses leading to bone remodeling is not fully understood. The earliest cellular response detected in mechanically stimulated osteoblasts is an increase in intracellular calcium concentration ([Ca2+]i). In this study, we used the clonal mouse osteoblast cell line MC3T3-E1 to show that uniaxial cyclic stretch induces: (1) an immediate increase in [Ca2+]i, and (2) the phosphorylation of critical osteoblast proteins that are implicated in cell proliferation, gene regulation, and cell survival. Our data suggest that cyclic stretch activates the phosphoinositide 3-kinase (PI3K) pathway including: PI3K, Akt, FKHR, and AFX. Moreover, cyclic stretch also causes the phosphorylation of stress-activated protein kinase/c-Jun N-terminal kinase. Attenuation in the level of phosphorylation of these proteins was observed by stretching cells in Ca2+-free medium, using intra- (BAPTA-AM) and extracellular (BAPTA) calcium chelators, or gadolinium, suggesting that influx of extracellular calcium plays a significant role in the early response of osteoblasts to mechanical stimuli

Loss of idealism or realistic optimism? A cross‐sectional analysis of dental hygiene students’ and registered dental hygienists’ professional identity perceptions

ObjectivesThe dental hygiene profession in the U.S. is in the process of establishing a direct access model of care and contributing to the creation of the profession of a dental therapist. The objectives were to analyse the professional role perceptions of dental hygiene students and registered dental hygienists in these times of change. Specifically, it was explored whether dental hygiene students’ current professional identities differ (i) from their expected future identities, and (ii) from dental hygienists’ current and (iii) past identities.MethodsSurvey data were collected from 215 dental hygiene students concerning their present and future role perceptions, and from 352 registered dental hygienists concerning their present and past professional identity perceptions.ResultsStudents’ future professional identity perceptions were even more positive than their very positive current perceptions of their professional role components. Students’ current perceptions of professional pride, professional ambition, work ethic and patient relations were more positive than dental hygienists’ current perceptions of these professional role components. A comparison of students’ current perceptions with dental hygienists’ current and retrospective descriptions showed that students were more positive than dental hygienists in each case.ConclusionsThe fact that dental hygienists had less positive role perceptions than dental hygiene students might lead to the conclusion that a loss of idealism occurs over the course of a professional lifespan. However, dental hygienists actually improved their role perceptions over time and students’ future descriptions were more positive than their current descriptions, supporting the interpretation that realistic optimism dominates professional role perceptions in these times of change.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141357/1/idh12287_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141357/2/idh12287.pd

Microscopic Enteritis; Clinical Features and Correlations with Symptoms

Aim: To assess the clinical characteristic of CD as well as correlation of symptoms and the degrees of intestinal mucosal lesions in Iranian children. Background: Microscopic Enteritis (Marsh 0-II) is associated with malabsorption. Patients and methods: From August 2005 to September 2009, 111 cases with malabsorption and classical gastrointestinal symptoms were evaluated. Results: The mean (±SD) age of children with CD was 4.9±3.5 years (range, 6 month - 16 years) and the mean duration of symptoms was 8 ± 20.5 months. 50 cases (45%) were female and 61 cases (55%) were male. The most common clinical presentation was failure to thrive in 72%, chronic diarrhea in 65.8% and Iron deficiency anemia in 59.5%. Sensitivity of EMA was 100% in patients with Marsh IIIb and Marsh IIIc. EMA was also positive in 77% of cases with Marsh 0, 18% in Marsh I, 44% in Marsh II and 81.8% in patients with Marsh IIIa. Conclusion: Histopathology did not reflect the severity of gluten sensitivity. This would suggest that the degree of intestinal mucosal damage might not be a reliable prognostic factor. Significant symptoms can be present with minor histological change on biopsy

Accuracy of rapid radiographic film calibration for intensity‐modulated radiation therapy verification

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135342/1/acm20086.pd

Toward a ground-motion logic tree for probabilistic seismic hazard assessment in Europe

The Seismic Hazard Harmonization in Europe (SHARE) project, which began in June 2009, aims at establishing new standards for probabilistic seismic hazard assessment in the Euro-Mediterranean region. In this context, a logic tree for ground-motion prediction in Europe has been constructed. Ground-motion prediction equations (GMPEs) and weights have been determined so that the logic tree captures epistemic uncertainty in ground-motion prediction for six different tectonic regimes in Europe. Here we present the strategy that we adopted to build such a logic tree. This strategy has the particularity of combining two complementary and independent approaches: expert judgment and data testing. A set of six experts was asked to weight pre-selected GMPEs while the ability of these GMPEs to predict available data was evaluated with the method of Scherbaum et al. (Bull Seismol Soc Am 99:3234-3247, 2009). Results of both approaches were taken into account to commonly select the smallest set of GMPEs to capture the uncertainty in ground-motion prediction in Europe. For stable continental regions, two models, both from eastern North America, have been selected for shields, and three GMPEs from active shallow crustal regions have been added for continental crust. For subduction zones, four models, all non-European, have been chosen. Finally, for active shallow crustal regions, we selected four models, each of them from a different host region but only two of them were kept for long periods. In most cases, a common agreement has been also reached for the weights. In case of divergence, a sensitivity analysis of the weights on the seismic hazard has been conducted, showing that once the GMPEs have been selected, the associated set of weights has a smaller influence on the hazar