Evaluation of open pit slope stability using various slope angles and element types

Purpose. The objective of this study is to demonstrate a method to select the optimal slope angle related to three principal factors: safety, productivity and mining costs. Also, it aims to investigate the accuracy of numerical analysis using different element types and order. Methods. Series of two-dimensional elasto-plastic finite-element models has been constructed at various slope angles (e.g. 40°, 45°, 50°, 55°, 60°, 65°, and 70°) and different element types (e.g. 3-noded triangle (T3), 6-noded triangle (T6), 4-noded quadrilateral (Q4) and 8-noded quadrilateral (Q8).The results are presented, discussed and compared at various slope angles and element types in terms of critical strength reduction factor (CSRF) or its equivalent factor of safety (FOS), total rock slope displacement, mine production and mining costs. Findings. The results reveal that, the mine productivity increases as slope angle increases, however, slope stability deteriorates. Alternatively, the factor of safety (FOS) decreases as slope angle becomes steeper (e.g. minimum factor of safety is obtained at highest steep angle of 70°). Despite of the increasing in computation time, the analysis shows that, the accuracy of the modelling increases when adopting high-order element types (e.g. 8-noded quadrilateral and 6-noded triangle elements). Originality. This study provides a methodology for the application of the numerical modelling methods on open pit mine. As a result, the mine planners will be able to know ahead of time the optimal slope angle with respect to safety, production and mining costs. Practical implications. This study sheds light on the usefulness of adopting numerical modelling analysis in the feasibility studies to determine and compare mining costs against safety and slope angle.Мета. Розробка методики для підбору оптимального кута нахилу борта кар’єру з видобутку мідно-нікелевих руд з урахуванням трьох головних чинників: безпека, продуктивність та витрати, а також перевірка точності чисельного аналізу при використанні елементів різного типу і порядку. Методика. Побудовано серії двовимірних пружно-пластичних кінцево-елементних моделей (КЕМ) для різних кутів нахилу борта кар’єру (наприклад, 40°, 45°, 50°, 55°, 60°, 65° і 70°) та з елементами різного типу (3-вузловий трикутник (T3), 6-вузловий трикутник (T6), 4-вузловий чотирикутник (Q4) і 8-вузловий чотирикутник (Q8)). Чисельне моделювання виконано у програмному продукті Rock and Soil 2-Dimensional Analysis Program. В якості критерію руйнування прийнято критерій міцності Кулона-Мора. Результати. Дослідження показали, що продуктивність шахти зростає зі збільшенням кута нахилу борта кар’єру; однак при цьому зменшується його стійкість, і навпаки, чим крутіше кут нахилу борта, тим менше коефіцієнт безпеки. Так, мінімальному значенню коефіцієнта безпеки відповідає найбільший кут нахилу 70°. Незважаючи на більш тривалі обчислення, аналіз показав, що точність моделювання зростає при використанні елементів високого порядку (8-вузлового чотирикутника і 6-вузлового трикутника). Наукова новизна. Розроблено новий методичний підхід для застосування чисельного моделювання для оцінки стійкості бортів кар’єрів з точки зору граничного коефіцієнта зниження міцності або його еквівалентного коефіцієнта безпеки, загального зсуву схилів, продуктивності та витрат на видобуток. Практична значимість. Дослідження доводять ефективність застосування чисельного моделювання для визначення доцільності витрат при різних кутах нахилу борта для забезпечення безпеки робіт. В результаті його застосування проектувальники кар’єрів зможуть заздалегідь спланувати оптимальний кут нахилу борта з урахуванням безпеки, продуктивності і витрат.Цель. Разработка методики для подбора оптимального угла наклона борта карьера по добыче медно-никелевых руд с учетом трех главных факторов: безопасность, производительность и затраты, а также проверка точности численного анализа при использовании элементов различного типа и порядка. Методика. Построены серии двумерных упругопластических конечно-элементных моделей (КЭМ) для разных углов наклона борта карьера (например, 40°, 45°, 50°, 55°, 60°, 65° и 70°) и с элементами разного типа (3-узловой треугольник (T3), 6-узловой треугольник (T6), 4-узловой четырехугольник (Q4) и 8-узловой четырехугольник (Q8)). Численное моделирование выполнено в программном продукте Rock and Soil 2-Dimensional Analysis Program. В качестве критерия разрушения принят критерий прочности Кулона-Мора. Результаты. Исследования показали, что производительность шахты растет с увеличением угла наклона борта карьера, однако при этом уменьшается его устойчивость, и наоборот, чем круче угол наклона борта, тем меньше коэффициент безопасности. Так, минимальному значению коэффициента безопасности соответствует самый большой угол наклона 70°. Несмотря на более длительные вычисления, анализ показал, что точность моделирования возрастает при использовании элементов высокого порядка (8-узлового четырехугольника и 6-узлового треугольника). Научная новизна. Разработан новый методический подход для применения численного моделирования для оценки устойчивости бортов карьеров с точки зрения предельного коэффициента снижения прочности или его эквивалентного коэффициента безопасности, общего смещения склонов, производительности и затрат на добычу. Практическая значимость. Исследования доказывают эффективность применения численного моделирования для определения целесообразности затрат при различных углах наклона борта для обеспечения безопасности работ. В результате его применения проектировщики шахт смогут заранее спланировать оптимальный угол наклона борта с учетом безопасности, производительности и затрат.The authors acknowledge the support of Rocscience Inc. for getting a free two-week full-version of RS2D (Rock-Soil two-dimensional finite-element analysis program). The authors are grateful for their support

Anodische Elektrofermentation von Acetoin in Escherichia coli

Anodische Elektrofermentation ist eine neue Strategie anaerober Biotechnologie. Sie ermöglicht Umsetzungen, bei denen die mittlere Oxidationsstufe des Endproduktes höher ist als die des Substrats. Konventionell werden solche Reaktionen ausschließlich unter oxischen Prozessbedingungen katalysiert. Dies geht mit einer starken Biomassebildung und einem hohem Energieaufwand einher. Bei der Elektrofermentation fällt stattdessen als Nebenprodukt lediglich elektrische Energie an, welche universell verwendet werden kann. Ziel dieser Arbeit war die Etablierung eines Systemes zur Elektrofermentation von Acetoin in einem metabolisch veränderten Escherichia coli Stamm. Bei Acetoin handelt es sich um einen vielversprechenden Kandidaten für Basischemikalien einer anvisierten Bioökonomie. Im ersten Teil der Arbeit konnte ein funktionales System zur Elektrofermentation von Acetoin in Escherichia coli etabliert werden. Darauf aufbauend wurde im zweiten Teil der Arbeit das Reaktorsystem dahingehend weiterentwickelt, den Anforderungen dieses speziellen Fermentationsprozesses Rechnung zu tragen und inhibierende Faktoren zu identizieren und zu eliminieren. Im dritten Teil der Arbeit wurden Untersuchungen zur Physiologie des Produktionsstammes vorgenommen und die gewonnenen Erkenntnisse über die Acetyl-Phosphat abhängige Stowechselregulation zur Beschleunigung der metabolischen Rate angewandt. Im letzten Charakterisierungsschritt konnte die Leistungsgrenze des Reaktorsystems ermittelt und eine Modellbetrachtung des Fermentationsprozesses angestellt werden. Es konnte hierdurch ein Fermentationsprozess etabliert werden, welcher Acetoin mit einer Ausbeute von rund 80 % des theoretischen Maximums produziert. Ferner wurde eine Steigerung der Umsatzrate um das 15-Fache erreicht. Mit einer Produktivität von 76 mg l−1 h werden erstmals Werte erreicht, die eine zukünftige Konkurrenz zu oxischen Fermentationen plausibel erscheinen lassen

Accelerated Electro-Fermentation of Acetoin in Escherichia coli by Identifying Physiological Limitations of the Electron Transfer Kinetics and the Central Metabolism

Anode-assisted fermentations offer the benefit of an anoxic fermentation routine that can be applied to produce end-products with an oxidation state independent from the substrate. The whole cell biocatalyst transfers the surplus of electrons to an electrode that can be used as a non-depletable electron acceptor. So far, anode-assisted fermentations were shown to provide high carbon efficiencies but low space-time yields. This study aimed at increasing space-time yields of an Escherichia coli-based anode-assisted fermentation of glucose to acetoin. The experiments build on an obligate respiratory strain, that was advanced using selective adaptation and targeted strain development. Several transfers under respiratory conditions led to point mutations in the pfl, aceF and rpoC gene. These mutations increased anoxic growth by three-fold. Furthermore, overexpression of genes encoding a synthetic electron transport chain to methylene blue increased the electron transfer rate by 2.45-fold. Overall, these measures and a medium optimization increased the space-time yield in an electrode-assisted fermentation by 3.6-fold

Electrode-assisted acetoin production in a metabolically engineered Escherichia coli strain

Background This paper describes the metabolic engineering of Escherichia coli for the anaerobic fermentation of glucose to acetoin. Acetoin has well-established applications in industrial food production and was suggested to be a platform chemical for a bio-based economy. However, the biotechnological production is often hampered by the simultaneous formation of several end products in the absence of an electron acceptor. Moreover, typical production strains are often potentially pathogenic. The goal of this study was to overcome these limitations by establishing an electrode-assisted fermentation process in E. coli. Here, the surplus of electrons released in the production process is transferred to an electrode as anoxic and non-depletable electron acceptor. Results In a first step, the central metabolism was steered towards the production of pyruvate from glucose by deletion of genes encoding for enzymes of central reactions of the anaerobic carbon metabolism (ΔfrdA-D ΔadhE ΔldhA Δpta–ack). Thereafter, the genes for the acetolactate synthase (alsS) and the acetolactate decarboxylase (alsD) were expressed in this strain from a plasmid. Addition of nitrate as electron acceptor led to an anaerobic acetoin production with a yield of up to 0.9 mol acetoin per mol of glucose consumed (90% of the theoretical maximum). In a second step, the electron acceptor nitrate was replaced by a carbon electrode. This interaction necessitated the further expression of c-type cytochromes from Shewanella oneidensis and the addition of the soluble redox shuttle methylene blue. The interaction with the non-depletable electron acceptor led to an acetoin formation with a yield of 79% of the theoretical maximum (0.79 mol acetoin per mol glucose). Conclusion Electrode-assisted fermentations are a new strategy to produce substances of biotechnological value that are more oxidized than the substrates. Here, we show for the first time a process in which the commonly used chassis strain E. coli was tailored for an electrode-assisted fermentation approach branching off from the central metabolite pyruvate. At this early stage, we see promising results regarding carbon and electron recovery and will use further strain development to increase the anaerobic metabolic turnover rate

Extracellular reduction of solid electron acceptors by Shewanella oneidensis

Shewanella oneidensis is the best understood model organism for the study of dissimilatory iron reduction. This review focuses on the current state of our knowledge regarding this extracellular respiratory process and highlights its physiologic, regulatory and biochemical requirements. It seems that we have widely understood how respiratory electrons can reach the cell surface and what the minimal set of electron transport proteins to the cell surface is. Nevertheless, even after decades of work in different research groups around the globe there are still several important questions that were not answered yet. In particular, the physiology of this organism, the possible evolutionary benefit of some responses to anoxic conditions, as well as the exact mechanism of electron transfer onto solid electron acceptors are yet to be addressed. The elucidation of these questions will be a great challenge for future work and important for the application of extracellular respiration in biotechnological processes

Adult sex identification using digital radiographs of the proximal epiphysis of the femur at Suez Canal University Hospital in Ismailia, Egypt

AbstractSex identification is an important step toward establishing identity from unknown human remains. The study was performed to test accuracy of sex identification using digital radiography of proximal epiphysis of femur among known cross-sectional population at Suez Canal region. Seventy-two radiographs of femur of living non-pathologic individuals were included. Original sample was divided into two equal groups of females and males (24 each). Test sample (group 3) included 24 radiographs. Six landmarks (A–F) were selected and 15 distances were generated representing all possible combinations of these landmarks. A is a point on the shaft under lower end of lesser trochanter, B is a point on the shaft. A–B is perpendicular to the axis of the shaft. C and D are points on femoral neck. E and F are points on femoral head. In original sample, mean and standard deviation were calculated, then accuracy, sensitivity and specificity. In test sample, the 15 distances were used to identify sex of that radiograph according to the cut-off value made from original sample.In original sample, CE and EF were most distinctive measurements for sexual dimorphism. AB and CF showed least accuracy (66.7% and 70.8%). BF, CE and EF were most sensitive for identification.In test sample, CE and EF showed 100% accuracy. AB and CF showed least accuracy (54.2% and 62.5%). AC, AE, BC, BE, BF, CE and EF were most sensitive for identification.Digital radiography of femur can be an alternative measurement used in sex identification in Egyptian population

Comparison between multidetector computed tomography and hysterosalpingography in assessment of infertile couples

Objective: To compare the efficacy of multidetector CT (MDCT) with conventional X-ray hysterosalpingography (HSG) in the evaluation of infertile couples. Methods: Thirty-four patients with diagnosis of infertility, were evaluated with 4-row MDCT prior to HSG. All patients underwent diagnostic laparoscopy in the following period. Sensitivity, specificity, negative predictive value and positive predictive value of MDCT and HSG for the detection of tubal obstruction and pelvic adhesions were calculated. Results: Mean duration of the procedure for HSG and MDCT respectively was 26 ± 3.3 and 7 ± 1.1 min. MDCT has shown significantly less patient discomfort and mean effective dose of radiation. MDCT was able to diagnose a case of adenomyosis and a case of ovarian tumor further to HSG. HSG diagnosed two cases of unilateral tubal block, four cases of bilateral tubal block and six cases were suggested as pelvic adhesions due to abnormal smearing at the second film. MDCT diagnosed one case of unilateral tubal block, four cases of bilateral tubal block being unable to detect pelvic adhesions because of lack of delayed imaging. Using laparoscopy as a reference standard; sensitivity, specificity, positive predictive value and negative predictive value of MDCT and HSG in detecting tubal block were as follows: (100%, 96.7%, 83.3% and 100% for MDCT in comparison to 100%, 93.7%, 66.7% and 100% for HSG. Sensitivity, specificity, positive predictive value and negative predictive value of HSG in detecting pelvic adhesions were 42.8%, 88.8%, 50%, and 85.7. Conclusion: This study demonstrated the feasibility of evaluating the female reproductive system by MDCT

A Shuttle-Vector System Allows Heterologous Gene Expression in the Thermophilic Methanogen Methanothermobacter thermautotrophicus ΔH

Thermophilic Methanothermobacter spp. are used as model microbes to study the physiology and biochemistry of the conversion of molecular hydrogen and carbon dioxide into methane (i.e., hydrogenotrophic methanogenesis). Yet, a genetic system for these model microbes was missing despite intensive work for four decades. Here, we report the successful implementation of genetic tools for Methanothermobacter thermautotrophicus ΔH. We developed shuttle vectors that replicated in Escherichia coli and M. thermautotrophicus ΔH. For M. thermautotrophicus ΔH, a thermostable neomycin resistance cassette served as the selectable marker for positive selection with neomycin, and the cryptic plasmid pME2001 from Methanothermobacter marburgensis served as the replicon. The shuttle-vector DNA was transferred from E. coli into M. thermautotrophicus ΔH via interdomain conjugation. After the successful validation of DNA transfer and positive selection in M. thermautotrophicus ΔH, we demonstrated heterologous gene expression of a thermostable β-galactosidase-encoding gene (bgaB) from Geobacillus stearothermophilus under the expression control of four distinct synthetic and native promoters. In quantitative in-vitro enzyme activity assay, we found significantly different β-galactosidase activity with these distinct promoters. With a formate dehydrogenase operon-encoding shuttle vector, we allowed growth of M. thermautotrophicus ΔH on formate as the sole growth substrate, while this was not possible for the empty-vector control. IMPORTANCE The world economies are facing permanently increasing energy demands. At the same time, carbon emissions from fossil sources need to be circumvented to minimize harmful effects from climate change. The power-to-gas platform is utilized to store renewable electric power and decarbonize the natural gas grid. The microbe Methanothermobacter thermautotrophicus is already applied as the industrial biocatalyst for the biological methanation step in large-scale power-to-gas processes. To improve the biocatalyst in a targeted fashion, genetic engineering is required. With our shuttle-vector system for heterologous gene expression in M. thermautotrophicus, we set the cornerstone to engineer the microbe for optimized methane production but also for production of high-value platform chemicals in power-to-x processes

MOESM4 of Electrode-assisted acetoin production in a metabolically engineered Escherichia coli strain

Additional file 4: Table S4. Summary of growth experiments: Âľ and final optical density