Improving workability of cement paste backfill using new binders

In this study effects of binder type and content and curing time on the compressive strength development of cement paste backfill (CPB) is investigated. Moreover, the effects of binder type and content and water content on the rheological properties of CPB material were studied. To undertake an experimental study, tailings of a copper mine in South Australia are mixed with binder and water. A new slag-cement called Mine Cement (MC) and ordinary Portland cement (PC) are used as the primary binder materials. Furthermore, fly ash (FA) is used as an additive to reduce the amount of the cement. Some CPB samples were cured under pressure to be more representative of the field conditions. MC exhibited better performance that PC regarding compressive strength development. Fly ash improved the compressive strength of CPB. However, this binder observed to be much less cementitious compare to MC. Strength performance of the CPB sample significantly improved when there were cured under pressure. Based on the results obtained from the test undertaken using a rheometer, it was found that increasing the water content results in lower yield stress. The results also show that MC improves the rheological properties of the CPB

Nutritional and metabolic characteristics of critically ill patients admitted for severe toxidermia.

Drug-induced toxidermia is an idiosyncratic adverse skin reaction that may become life-threatening in a small portion of patients, requiring intensive care unit (ICU) admission. The treatment recommendations are extrapolated from those of major burns, while prospective data remain sparse. The objective was to observe the application of these recommendations in patients treated in a burn ICU. Retrospective cohort study including patients requiring ICU between 2006 and 2020 in a tertiary university hospital. Age >18 years. Patients were categorized as Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN), or other toxidermia. severity scores, body surface area (BSA) involvement, nutritional and metabolic variables, trace element status, outcome variables. Descriptive statistics: median [IQR]. Altogether 35 patients were included (27 SJS/TEN and 8 "other"), aged 58 [48; 69] years. Skin involvement was 45% [30; 60] of body surface, 17 patients required mechanical ventilation, and length of ICU stay was 16 [6.5; 26] days. Hospital mortality was 23%. Fluid resuscitation requirements were moderate, despite intense inflammation (admission CRP (144 [89; 218] mg/L). The first 2 weeks' energy and protein intakes were below recommendations (p < 0.0001), lowest with oral feeding. Indirect calorimetry showed high energy expenditure in 11 patients (30.4 [23.9; 35.5] kcal/kg) resulting in negative energy balances (mean -245 kcal/day). Copper and zinc levels were below reference range during the first week, the low copper values being a novel finding. Trace elements should be monitored. The cohort was underfed with intakes lower than our ICU protocols, partly explained by short intubation times, and mucocutaneous involvement complicating the management and placement of feeding tubes. Oral feeding was least efficient and may become an indication for supplemental parenteral nutrition in the absence of an enteral feeding tube. gov Identifier: NCT05320653

Diabetic Foot Due to Anaphylactic Shock: A Case Report

Introduction: Diabetic foot is a clinical disorder, which is commonly seen in patients with diabetes mellitus. It is also the major cause of below knee amputation in the world. There are many underlying causes such as neuropathic, ischemic, and infectious causes for diabetic foot. Local or systemic complications may develop after snake bite. Case Presentation: We reported a very rare case, involving a 78-year-old male admitted to the Emergency Department, who developed anaphylactic shock and diabetic foot after the snake bite. Conclusions: Reviewing the literature, this is the second reported case of snake bite associated with diabetic foot

A physical modeling-based study on the control mechanisms of Negative Poisson's ratio anchor cable on the stratified toppling deformation of anti-inclined slopes

Available online 9 January 2021With ongoing increases in excavation depth, the large-scale toppling instability failure of stratified anti-inclined slopes is gaining wide attention. To address the problem of controlling toppling deformation failure of antiinclined slopes with traditional small-deformation materials, this paper takes the results of existing studies on the extraordinary mechanical properties of engineering-scale Negative Poisson’s ratio (NPR) anchor cable as a theoretical basis, and develops a model-scale NPR anchor cable according to similarity theory. Relying on a selfdeveloped “engineering disaster model experimental system”, a physical modeling-based experiment to explore the reinforcement mechanism of stratified anti-inclined slope using model-scale NPR and ordinary anchor cables is performed. The physical model is monitored using static strain data acquisition equipment, an infrared thermal imager, tension sensors, and digital speckle correlation method (DSCM) displacement field measurement equipment. The evolution of the displacement field, strain field, temperature field, and anchor cable force are obtained during excavation on the physical model. By comparing the evolution of these parameters with images from both the anti-inclined slope model instability failure test and the deformation characteristics on the two sides of the slope, which were reinforced using different types of anchor cables, this paper determines the mechanisms governing instability failure of anti-inclined slopes reinforced with NPR anchor cable. In addition, this paper also proves that NPR anchor cable can be used to monitor the sliding force of anti-inclined slopes throughout excavation, and lays a foundation for the application of NPR anchor cable monitoring technology to the advanced anti-inclined slope failure warning.Zhigang Tao, Chun Zhu, Manchao He, Murat Karaku

A kinetic study of mercury(II) transport through a membrane assisted by new transport reagent

Background: A new organodithiophosphorus derivative, namely O-(1,3-Bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate, was synthesized and then the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated.Results: The compound 1 was characterized by elemental analysis, IR, H-1 and P-31 NMR spectroscopies. The transport of mercury(II) ion by a zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. The compound 1 is expected to serve as a model liquid membrane transport with mercury(II) ions.Conclusion: A kinetic study of mercury(II) transport through a membrane assisted by O-(1,3-Bispiperidino-2-propyl)4-methoxy phenyldithiophosphonate was performed. It can be concluded that the compound 1 can be provided a general and straightforward route to remove toxic metals ions such as mercury(II) ion from water or other solution

Effect of Loading Rate and Time Delay on the Tangent Modulus Method (TMM) in Coal and Coal Measured Rocks

Non-destructive techniques of in-situ stress measurement from oriented cored rocks have great potential to be developed as a cost cost-efective and reliable alternative to the conventional overcoring and hydraulic fracturing methods. The tangent modulus method (TMM) is one such technique that can be applied to oriented cored rocks to measure in-situ stresses. Like the deformation rate analysis (DRA), the rock specimen is subjected to two cycles of uniaxial compression and the stresstangent modulus curve for the two cycles is obtained from the stress–strain curve. A bending point in the tangent modulus curve of the frst cycle is observed, separating it from the tangent modulus curve of the second cycle. The point of separation between the two curves is assumed to be the previously applied maximum stress. A number of experiments were conducted on coal and coal measured rocks (sandstone and limestone) to understand the efect of loading conditions and the time delay. The specimens were preloaded, and cyclic compressions were applied under three diferent modes of loading, four diferent strain rates, and time delays of up to one week. The bending point in the stress-tangent modulus curves occurred approximately at the applied pre-stress levels under all three loading modes, and no efect of loading rate was observed on the bending points in TMM. However, a clear efect of time delay was observed on the TMM, contradicting the DRA results. This could be due to the sensitivity of TMM and the range of its applicability, all of which need further investigation for the in-situ stress measurement.Zulfqar Ali, Murat Karakus, Giang D. Nguyen, Khalid Amrouc

Some reactions of 2-(4-substitutedphenyl)-2-(N-methyl-N-4-substitutedbenzamido) acetic acids

In situ generated 2,4-diaryl substituted münchnones from 2-(4-substitutedphenyl)-2-(N-methyl-N-4-substitutedbenzamido)acetic acids react with acetic anhydride in the presence of 2-nitromethylene thiazolidine, which is most likely acting as a base, and unexpectedly undergo a Dakin–West type reaction and a concurrent autoxidation reaction leading to the formation of (E)-1-(N,4-dimethylbenzamido)-1-(4-fluorophenyl)prop-1-en-2-yl acetate, 4-substitutedphenyl-N-methyl-N-(4-substitutedbenzoyl) benzamides and p-substituted benzoic acids. In addition, a novel and efficient access to N-acyl urea derivatives is described by the reaction between 2-(4-substitutedphenyl)-2-(N-methyl-N-4-substitutedbenzamido)acetic acids and cyclohexyl, isopropyl carbodiimides in the presence of a base. The structures of all new products were identified on the basis of NMR and IR spectra, along with X-ray diffraction data and HRMS measurements

Application of slag–cement and fly ash for strength development in cemented paste backfills

The present study investigates the combined capacity of a newly developed slag-blended cement (MC) and fly ash (FA) as a sustainable solution towards improving the mechanical performance of the cemented paste backfill (CPB) system of a copper-gold underground mine. A total of thirteen mix designs consisting of three MC-treated and ten MC + FA-treated blends were examined. Samples were prepared with a solids content of 77% (by total mass), and were allowed to cure for 7, 14, 28, 56 and 128 days prior unconfined compression testing. Scanning electron microscopy (SEM) studies were also carried out to observe the evolution of fabric in response to MC and MC + FA amendments. The greater the MC content and/or the longer the curing period, the higher the developed strength, toughness and stiffness. The exhibited improvements, however, were only notable up to 56 days of curing, beyond of which the effect of curing was marginal. The performance of 4% Portland cement or PC (by total dry mass) was found to be similar to that of 1.5% MC, while the higher MC inclusions of 2.5% and 3%, though lower in terms of binder content, unanimously outperformed 4% PC. The use of FA alongside MC improved the bonding/connection interface generated between the tailings aggregates, and thus led to improved mechanical performance compared with similar MC inclusions containing no FA. Common strength criteria for CPBs were considered to assess the applicability of the newly introduced MC and MC + FA mix designs. The mix designs “3% MC” and “2.5% MC + 2–2.5% FA” satisfied the 700 kPa strength threshold required for stope stability, and thus were deemed as optimum design choices.Yue Zhao, Amin Soltani, Abbas Taheri, Murat Karakus and An Den