Evaluation of rock stability challenges affecting the formation of sustainable pit lake towards mine closure following crown pillar extraction in open pit-underground mines.

The extraction of high-grade ore from the crown pillar (CP) in open pit-underground mines poses stability challenges and potential environmental risks. While an open pit has the potential to transition into a pit lake, the extraction of CP can induce failure in the surrounding walls, preventing the formation of the lake. There is also a concern that the backfilling material may not effectively confine toxic water within the pit, thereby risking contamination of the underground environment. To address these issues, a case study was conducted using FLAC3D and 3DEC models to evaluate the extent of failure caused by CP extraction. On-site observation, along with modelling, has revealed rock damage, including deformation stretching about 4 m from the pit wall and extending vertically from the pit floor to the ramp. The study identified three primary factors leading to pit wall failure or damage: steep pit slopes reaching approximately 70° near the pit floor, an underestimated CP thickness by about 4 m, and the concurrent extraction of ore from the pit wall alongside CP. Based on these findings, rehabilitation measures are suggested, including excavation of the deformed wall and cantilever, as well as partial pit backfilling. There is a substantial increase in the volume of backfill material as the extent of failure increases, which raise concerns about the decision-making process regarding CP extraction. Therefore, this article aims to raise environmental awareness and evaluate whether the benefits of ore extraction outweigh the considerations for pit wall support and the rehabilitation efforts during mine closure.

Backfilling cohorts in phase I dose-escalation studies.

BACKGROUND: The use of 'backfilling', assigning additional patients to doses deemed safe, in phase I dose-escalation studies has been used in practice to collect additional information on the safety profile, pharmacokinetics and activity of a drug. These additional patients help ensure that the maximum tolerated dose is reliably estimated and give additional information to determine the recommended phase II dose. METHODS: In this article, we study the effect of employing backfilling in a phase I trial on the estimation of the maximum tolerated dose and the duration of the study. We consider the situation where only one cycle of follow-up is used for escalation as well as the case where there may be delayed onset toxicities. RESULTS: We find that, over a range of scenarios, the use of backfilling gives an increase in the percentage of correct selections by up to 9%. On average, for a treatment with a cycle length of 6 weeks, each additional backfilling patient reduces the trial duration by half a week. CONCLUSIONS: Backfilling in phase I dose-escalation studies can substantially increase the accuracy of estimation of the maximum tolerated dose, with a larger impact in the setting with a dose-limiting toxicity event assessment period of only one cycle. This increased accuracy and reduction in the trial duration are at the cost of increased sample size.

Highly Uniform DNA Monolayers Generated by Freezing-Directed Assembly on Gold Surfaces Enable Robust Electrochemical Sensing in Whole Blood.

Assembling DNA on solid surfaces is fundamental to surface-based DNA technology. However, precise control over DNA conformation and organization at solid-liquid interfaces remains a challenge, resulting in limited stability and sensitivity in biosensing applications. We herein communicate a simple and robust method for creating highly uniform DNA monolayers on gold surfaces by a freeze-thawing process. Using Raman spectroscopy, fluorescent imaging, and square wave voltammetry, we demonstrate that thiolated DNA is concentrated and immobilized on gold surfaces with an upright conformation. Moreover, our results reveal that the freezing-induced DNA surfaces are more uniform, leading to improved DNA stability and target recognition. Lastly, we demonstrate the successful detection of a model drug in undiluted whole blood while mitigating the effects of biofouling. Our work not only provides a simple approach to tailor the DNA-gold surface for biosensors but also sheds light on the unique behavior of DNA oligonucleotides upon freezing on the liquid-solid interface.

Diversification of CORVET tethers facilitates transport complexity in Tetrahymena thermophila.

In endolysosomal networks, two hetero-hexameric tethers called HOPS and CORVET are found widely throughout eukaryotes. The unicellular ciliate Tetrahymena thermophila possesses elaborate endolysosomal structures, but curiously both it and related protozoa lack the HOPS tether and several other trafficking proteins, while retaining the related CORVET complex. Here, we show that Tetrahymena encodes multiple paralogs of most CORVET subunits, which assemble into six distinct complexes. Each complex has a unique subunit composition and, significantly, shows unique localization, indicating participation in distinct pathways. One pair of complexes differ by a single subunit (Vps8), but have late endosomal versus recycling endosome locations. While Vps8 subunits are thus prime determinants for targeting and functional specificity, determinants exist on all subunits except Vps11. This unprecedented expansion and diversification of CORVET provides a potent example of tether flexibility, and illustrates how 'backfilling' following secondary losses of trafficking genes can provide a mechanism for evolution of new pathways.This article has an associated First Person interview with the first author of the paper.

Bladder Backfilling versus Standard Catheter Removal for Trial of Void after Outpatient Laparoscopic Gynecologic Surgery: A Systematic Review and Meta-Analysis.

OBJECTIVE: To compare the rate of postoperative urinary retention and time to discharge between bladder backfilling and standard catheter removal for trial of void (TOV) after outpatient laparoscopic gynecologic surgery. Our secondary objectives were to compare the time to void, postoperative complications, and patient satisfaction. DATA SOURCES: We searched the PubMed, Ovid MEDLINE, Embase, Cochrane Library databases, and relevant reference lists of eligible articles up to March of 2021. METHODS OF STUDY SELECTION: This review included randomized controlled trials (RCTs) of TOV after outpatient laparoscopic gynecologic surgery. Odds ratios (ORs) with 95% confidence interval (CI) and weighted mean differences (WMDs) were reported. The quality of the studies was assessed according to the Cochrane Handbook for Systematic Reviews of Interventions. Data were analyzed with Review Manager 5.4 software (RevMan 5.4.1; Cochrane Collaboration, London, United Kingdom). TABULATION, INTEGRATION, AND RESULTS: Five RCTs (N = 488) were included. The bladder backfilling group had a significantly shorter time to void than the standard TOV group (WMD, -25.19 minutes; 95% CI, -44.60 to -5.77; p = .01). Successful TOV was not significantly different between the 2 (OR, 0.92; 95% CI, 0.51 to -1.65; p = .77), without significant heterogeneity (I2 = 24%). There was also no significant difference in the time to discharge between the 2 TOV techniques (WMD, -25.19 minutes; 95% CI, -44.60 to -5.77; p = .01). There was no significant difference in complication rates or patient satisfaction between the 2 groups. CONCLUSION: The bladder backfilling technique of TOV after outpatient laparoscopic gynecologic surgery may reduce the time to first spontaneous void without affecting patient satisfaction or postoperative complications, but it does not significantly affect the time to discharge or urinary retention.

Water runoff harvesting systems for restoration of degraded rangelands: A review of challenges and opportunities.

Mismanagement of rangelands worldwide has accelerated processes of overland flow and soil erosion, resulting in extensive land degradation. Wherever self-restoration processes of degraded rangelands are hindered or negated, active recovery efforts, coupled with livestock pressure management, might be needed. The objective of this review paper is to provide land managers and environmental planners with applied and practical knowledge on advantages and disadvantages of the main methodologies and practices for runoff harvesting in rangelands. Preferably, restoration efforts should focus on forming low-footprint runoff harvesting systems on hillslopes which encompass the runoff's source area. These systems should imitate natural patchiness, strengthening source-sink relations, accelerating re-establishment of herbaceous and woody vegetation, maximizing the retaining of water on hillslopes, regulating hydrological connectivity, lessening soil erosion, and minimizing transmission of water to stream channels. The resulting lower-energy floods are expected to negate the need for massive check dams in channels. If flood dissipation in streams is still necessary, then high-to medium-porosity check dams, made of local materials, might be effective for lessening scour processes and sediment transport. Furthermore, in terms of environmental sustainability, a large number of pointed (e.g., branch bundles; brush or woody piles; micro-catchments) or low-to medium-footprint lineal means for regulating surface processes in hillslopes (e.g., stone terraces; contour furrows/trenches/ditches) and channels (e.g., log check dams; loose rock check dams; porous or semi-permeable rock check dams; gabions) are expected to be more cost-effective than a small number of massive means (e.g., contour bench terraces; earth bunds/dykes; concrete check dams). If runoff harvesting systems are properly designed, restoration processes over time are expected to generate geo-ecological feedbacks and recover eco-hydrological functioning, increasing pasture productivity and sustaining rangeland carrying capacity.

Rapid monitoring of reclaimed farmland effects in coal mining subsidence area using a multi-spectral UAV platform.

In eastern China, coal mining has damaged a large amount of farmland, posing a great threat to food security. Backfilling with coal waste, fly ash, and sediments from rivers is an effective method to restore farmland. This study was conducted at the reclaimed area (RA) and the undisturbed area (UA) in Shandong Province, China. Soil and plant analyzer development (SPAD) of corn was selected as an indicator of crop growth. Multi-spectral data was obtained by the unmanned aerial vehicle equipped with a camera. By analyzing the correlation between SPAD and spectral bands, the common vegetation index is improved. Different regression methods were used to construct the SPAD inversion model. The distribution of corn SPAD was monitored to objectively evaluate reclamation technology. The results are as follows: (1) the vegetation index improved using the red-edge band has a higher correlation with SPAD, and the largest coefficient of determination (R2) value is 0.779; (2) the optimum inversion model for both jointing stage (R2 = 0.676) and milky stage (R2 = 0.661) is the linear regression model; the optimum model for both tasseling stage (R2 = 0.809) and filling stage (R2 = 0.830) is the partial least squares regression model; (3) the SPAD inversion map of RA and UA obtained by the optimum model shows that the corn grown in RA is slightly better than in UA. This study realized the rapid and efficient monitoring of the reclamation effects based on multi-spectral imagery and verified the feasibility of backfilling reclamation with Yellow River sediment in coal mining subsidence areas.

From injury to full repair: nerve regeneration and functional recovery in the common octopus, Octopus vulgaris.

Spontaneous nerve regeneration in cephalopod molluscs occurs in a relative short time after injury, achieving functional recovery of lost capacity. In particular, transection of the pallial nerve in the common octopus (Octopus vulgaris) determines the loss and subsequent restoration of two functions fundamental for survival, i.e. breathing and skin patterning, the latter involved in communication between animals and concealment. The phenomena occurring after lesion have been investigated in a series of previous studies, but a complete analysis of the changes taking place at the level of the axons and the effects on the animals' appearance during the whole regenerative process is still missing. Our goal was to determine the course of events following injury, from impairment to full recovery. Through imaging of the traced damaged nerves, we were able to characterize the pathways followed by fibres during regeneration and end-target re-innervation, while electrophysiology and behavioural observations highlighted the regaining of functional connections between the central brain and periphery, using the contralateral nerve in the same animal as an internal control. The final architecture of a fully regenerated pallial nerve does not exactly mirror the original structure; however, functionality returns to match the phenotype of an intact octopus with no observable impact on the behaviour of the animal. Our findings provide new important scenarios for the study of regeneration in cephalopods and highlight the octopus pallial nerve as a valuable 'model' among invertebrates.

Effect of postoperative partial bladder filling after minimally invasive hysterectomy on postanesthesia care unit discharge and cost: a single-blinded, randomized controlled trial.

BACKGROUND: Hysterectomy is one of the most common surgical procedures performed each year with substantial related health care costs. This trial studied the effect of postoperative bladder backfilling to submicturition level in the operating room and its effect on early postoperative patient care and related cost. OBJECTIVE: The objective of the study was to compare the effect of bladder backfilling on early postoperative patient care and related cost. STUDY DESIGN: This was a randomized, single-blinded, controlled trial conducted between April 2016 and February 2017 at a single urban university hospital providing tertiary care for minimally invasive gynecologic surgery. Ninety-one patients undergoing straight-stick laparoscopic and robot-assisted hysterectomy by minimally invasive gynecologic surgeons for benign indications were recruited. The bladder was partially backfilled with 150 mL of normal saline postoperatively in the intervention group and drained in the control group, as per standard of care. Main outcomes studied were time needed to void, time spent in the postanesthesia care unit, and postanesthesia care unit cost after minimally invasive hysterectomy. Our secondary outcomes were postoperative complications. RESULTS: Forty-six patients (50.5%) were randomized to the intervention group, and 45 patients (49.5%) to the control group. Baseline comparative analysis of demographics and preoperative patient-specific variables, surgical history, intraoperative characteristics, and administered medications found the 2 groups to be largely homogenous. After regression analyses for adjustment, we found a significant reduction in the time needed to void, time spent in the postanesthesia care unit, and postanesthesia care unit-associated cost in the intervention group. Patients voided 64.9 minutes earlier than the control group (P = .015) ans spent 64 fewer minutes in the postanesthesia care unit (P = .006), resulting in $401.5 (USD) saving per patient (P = .006). None of the patients encountered any postoperative complications. CONCLUSION: Based on the findings of this randomized clinical trial, postoperative bladder backfilling to submicturition level shortens the time needed for patients to void in the postanesthesia care unit, resulting in shorter postanesthesia care unit stay and resultant cost savings. Conservatively projecting our findings on minimally invasive hysterectomy procedure is estimated to result in $69 million to $139 million (USD) per year in savings. Initiating similar investigations in other ambulatory surgical fields will likely result in a more substantial impact.

A laboratory investigation on the performance of South African acid producing gold mine tailings and its possible use in mine reclamation.

This paper presents the results of laboratory investigations conducted on gold mine tailings (GMT) to assess their chemical, mineralogical and geotechnical characteristics in view of assessing its suitability as an alternative backfilling solution in mine reclamation. Chemical characterization revealed that GMT is dominated by Si, Al, and Fe with notable amounts of Cr, Zr, Zn, Pb, Ce, As, Ba, Ni, V, Sr, Nd, Cu, U, and Co. Mineralogical characterization revealed a composition of silicate minerals with secondary minerals such as jarosite, goethite and hematite. GMT composites showed improved strength characteristics. The particle sizes of the tailings are capable of producing a good paste fill that will require lower water-cement ratio. Moreover, the plasticity of the tailings provide for a likelihood for shear resistance to sliding in fluvial conditions. Curing and addition of cement showed positive effects on the compressive strength and shear strength of the tailings. However, the effect of curing and cement addition on the compaction characteristics and permeability of the tailings were negligible. GMT showed favorable characteristics for use in mine backfilling; it would be interesting to evaluate higher cement ratios to improve the characteristics of the tailings.

Deformation of Mesoporous Titania Nanostructures in Contact with D2 O Vapor.

For many applications, mesoporous titania nanostructures are exposed to water or need to be backfilled via infiltration with an aqueous solution, which can cause deformations of the nanostructure by capillary forces. In this work, the degree of deformation caused by water infiltration in two types of mesoporous, nanostructured titania films exposed to water vapor is compared. The different types of nanostructured titania films are prepared via a polymer template assisted sol-gel synthesis in conjunction with a polymer-template removal at high-temperatures under ambient conditions versus nitrogen atmosphere. Information about surface and inner morphology is extracted by scanning electron microscopy and grazing incidence small-angle neutron scattering (GISANS) measurements, respectively. Furthermore, complementary information on thin film composition and porosity are probed via X-ray reflectivity. The backfilling induced deformation of near surface structures and structures inside the mesoporous titania films is determined by GISANS before and after D2 O infiltration. The respective atmosphere used for template removal influences the details of the titania nanostructure and strongly impacts the degree of water induced deformation. Drying of the films shows reversibility of the deformation.

Application of mine water leaching protocol on coal fly ash to assess leaching characteristics for suitability as a mine backfill material.

Over the years, coal mining in the Mpumalanga Province of South Africa has negatively affected the environment by causing pollution of water resources, land subsidence and spontaneous coal combustion. Previous studies show that in-situ treatment of acid mine drainage (AMD) using coal fly ash (CFA) from local power stations was possible and sludge recovered out of such treatment can be used to backfill mines. In this article, the authors have attempted to understand the leaching characteristics of CFA when placed underground as a backfill material using the mine water leaching protocol (MWLP). The results show that the migration of contaminants between the coal fly ash and the AMD in the mine voids depends on the pH and quality of the mine water. While backfilling mine voids with CFA can neutralize and scavenge between 50% and 95% of certain environmentally sensitive elements from AMD such as Fe, Al, Zn, Cu, Ni, Co and Mn. At this moment, it is also important to point out that certain scavenged/removed contaminants from the AMD during initial phases of backfilling can be remobilized by the influx of acidic water into the mine voids. It has therefore been concluded that, while CFA can be used to backfill mine voids, the influx of fresh acidic mine water should be avoided to minimize the remobilization of trapped contaminants such as Fe, Al, Mn and As. However, the pozzolanic material resulting from the CFA-AMD interaction could prevent such influx.

Geotechnical properties of products of alternative fuel combustion and co-firing with hard coal in the context of their use as solidifying dense mixtures.

Efforts directed to reduction of greenhouse gas emissions have led to the introduction of new firing/co-firing technologies and alternative fuels in the coal-based power industry. This has resulted in the formation of combustion products with new properties that can affect the reuse of these wastes and/or pose a hazard to the environment. One of the power-plant fly ash (FA) reuse options is its application as a solidifying dense mixture with water for backfilling mine workings or in engineering constructions. In this comparative study, geotechnical properties of three groups of FA were evaluated: (i) weathered and freshly generated ash from hard coal combustion in conventional pulverized coal boilers without (C-PCA, C-PFA) and with selective non-catalytic reduction installations for NO x reduction (NC-PFA); (ii) FA from hard coal co-firing with alternative fuels: off gases (GC-PFA) or biomass (BC-PFA) in pulverized coal boilers; (iii) FA from coal (C-FFA) or biomass combustion (B-FFA) in fluidized-bed boilers. The transportability, bonding and solidification properties, uniaxial compression strength, and rewetting of dense mixtures were evaluated by measurements of volumetric density, fluidity, water retention capacity, bonding time, solidification time, uniaxial compression test, and slakeability at the background of the FA chemical composition. Calcareous C-FFA > B-FFA displayed the best geotechnical properties. Other materials showed poorer geotechnical properties than FFA and could be aligned in the order BC-PFA > GC-PFA > NC-PFA > C-PFA > C-PCA.

Reinforcement of Teeth Having Reenacted Perforating Internal Resorption Cavities After Repair Using Different Calcium Silicate-based Cements and Backfilling Materials: An In vitro Study.

To evaluate the fracture resistance (FR) of the teeth having reenacted perforating internal resorption cavities repaired by distinctive calcium silicate-based cements (CSCs) specifically: Endocem MTA, Biodentine, NeoMTA Plus, and backfilling materials. Ninety-six freshly extracted human mandibular premolar teeth were selected. Twelve roots were used as the negative control group. Rotary files were used to complete the final irrigation and root canal preparation on the remaining teeth. Following that, burs were used to make standardized internal resorption chambers in the middle part of the roots. Twelve of these samples were used as positive control samples. The remaining 72 root canals were obturated in the apical 4 mm using a single-cone approach, and they were separated into 6 groups based on the CSCs used to fill voids and the materials used as backfilling. Group 1: Endocem MTA (resorption) + Endocem MTA (coronal), Group 2: Endocem MTA (resorption) + Gutta-percha/sealer (coronal), Group 3: Biodentine (resorption) + Biodentine (coronal), Group 4: Biodentine (resorption) + Gutta-percha/sealer (coronal), Group 5: NeoMTA Plus (resorption) + NeoMTA Plus (coronal), and Group 6: NeoMTA Plus (resorption) + Gutta-percha/sealer (coronal). Specimens were inserted in acrylic resin and then subjected to fracture testing. Fracture strength tests were performed using a Universal Testing Machine. The force was employed vertically with a consistent speed of 1 mm/minute. The results were analyzed with Variance and Bonferrini tests at P < 0.005. The mean force of fracture values were 447.00, 201.25, 318.75, 187.50, 596.58, 258.75, 347.50, and 298.75 N for Group 1, 2, 3, 4, 5, 6, 7, and 8, respectively. "There was a significant difference (P < 0.001) between the experimental groups and the control group". Group 5 showed the highest FR as compared to other groups. Backfilling with CSCs appears to be a better material than a gutta-percha/sealer combination. Neo MTA plus furthermore appeared the highest fracture-resistant material, while Biodentine + Gutta percha/sealer showed the least FR.

Experimental Study and Application of Controlled Low-Strength Materials in Trench Backfilling in Suqian City, China.

When backfilling narrow spaces, controlled low-strength materials (CLSM) can be used to achieve an effective backfilling effect. The pipeline engineering in Yahnghe Avenue of Suqian, China, provides a favorable on-site condition for the use of CLSM. However, no guidance exists for the determination of the material mixture ratio of CLSM for this geological condition. Laboratory tests were performed to investigate the basic physical parameters of excavated soil and the optimal mixture ratio of CLSM. Results indicate that the sand and silt account for 29.76% and 57.23% of the weight of excavated soil, respectively. As the water content increases (from 40% to 50%), the flowability of the CLSM approximately shows a linear increase (slumps values from 154.3 mm to 269.75 mm for 9% cement content), while its compressive strength shows a linear decreasing trend (from 875.3 KPa to 468.3 KPa after curing for 28 days); as the cement content increases (from 6% to 12%), the flowability approximately shows a linear decreasing trend (from 238.8 mm to 178.5 mm for 45% water content), while the compressive strength shows a linear increasing trend (from 391.6 KPa to 987.6 KPa after curing for 28 days). By establishing the relationship between compressive strength/flowability and the water-cement ratio, the optimal material ratio is determined to be 9% cement content and 40-43% water content. The engineering application results indicate that the use of CLSM can achieve efficient and high-quality backfilling effects for pipeline trenches. The findings of this research may provide a reference for the application of CLSM in fields with similar geological conditions.

Experimental investigation on dynamic deformation characteristics of the overlying strata in backfilling strip mining at different time scales.

The dynamic subsidence disaster caused by underground mining of coal resources is a complex spatiotemporal process, which is a common disaster in mining areas. The backfilling strip mining technology is a green and sustainable coal mining method, which has been commonly used to reduce the subsidence disaster of the overlying strata and protect surface buildings. The transient deformation is the main reason of surface buildings damage; therefore, in this study, the similar material model was used to research dynamic deformation characteristics of the overlying strata in backfilling strip mining at different time scales, and the optical image method was employed to monitor and obtain the movement data of the overlying strata automatically. The data analysis shows that there is a time-scale effect in mining subsidence. The deformation of the overlying strata increases instantaneously at a certain time under the monitoring of small time scale, and this phenomenon gradually disappears as time scales increase. According to the subsidence velocity of small time scale, the subsidence state of the overlying strata can be further divided into the abrupt subsidence state and the gentle subsidence state. This is really significant for promoting the development of the backfilling strip mining technology and preventing the damage of surface buildings.

Mix proportion and microscopic characterization of coal-based solid waste backfill material based on response surface methodology and multi-objective decision-making.

The mix proportion of multi-source coal-based solid waste (CSW) for underground backfilling affects transportation and support performance of backfill materials, and even the backfilling cost. In this study, the optimal mix proportion of desulfurization gypsum (DG), furnace bottom slag (FBS) and gasification fine slag (GFS) is determined by the Response Surface Methodology-Box Behnken Design (RSM-BBD). Then the fluidity, bleeding rate, 3-day strength, 7-day strength and preparation cost are evaluation indicators, the optimal mix proportion of backfill materials is determined by the multi-objective decision-making method (MDM). Finally, the microstructure of the backfill material with optimal mix proportion was studied by TGA, MIP, SEM-EDS and XRD. The results show that the mix proportion of CSW with the optimal comprehensive index is coal gangue (CG): coal fly ash (CFA): DG: FBS: GFS = 1:1.5:0.2:0.1:0.1, the mass concentration is 78%, and ordinary Portland cement (OPC)/CSW = 7.5%. The weight loss phenomenon of the backfill material with the optimal mix proportion occurs continuously during the heating process, mainly due to the evaporation of crystal water, structural water and hydroxyl water. There are dense narrow-necked pores in the backfill material, and the pore connectivity is poor. There is no hydration reaction occurs between CSW particles, and the strength increase of the backfill material mainly depends on the hydration reaction of cement. In ettringite, part of Al2O3 is replaced by SiO2, and part of CaSO4 is replaced by CaCO3. This study provides a reference for the engineering application of underground backfilling with multi-source CSW.

Stress distribution and roof subsidence of surrounding strata considering in situ coal conversion and CO2 mineralization backfilling: Photoelastic experiments using 3D-printed models of mining faces and goafs.

Coal, a reliable and economical fuel, is expected to remain the primary energy source for power generation for the foreseeable future. However, conventional mining and utilization of coal has caused environmental degradation and infrastructure damage. An in situ coal conversion method has been proposed to mitigate environmental problems and reduce CO2 emissions resulting from coal extraction and utilization. This method involves the in situ conversion and utilization of coal, backfilling of waste rock, and CO2 mineralization to backfill the goaf. In this study, the impact of mining and conversion activities on the surrounding strata was evaluated to ascertain the effectiveness and advantages of the in situ coal conversion method. Transparent stope models were created using three-dimensional printing technology. The stress distribution and deformation characteristics of the surrounding strata were examined using photoelasticity and digital image correlation methods. The results were compared with those obtained using the traditional backfill mining method. The comparison revealed that the disturbance to the surrounding strata was 14.4 times less in the in situ conversion method than in the traditional backfill mining method. Additionally, the disturbance height at the roof and the disturbance depth at the floor were 4.2 and 2.1 times lower, respectively. The roof subsidence in the in situ conversion method was 1.97 times less than that in the traditional backfill mining method. These results confirm the advantages of minimizing the disturbance to surrounding rocks and controlling the subsidence of roof strata.

A design approach of panel size for the cooperative development of cropland protection and coal mining in a coal-cropland overlapping area.

Cropland is the foundation of food security. Coal is the guarantee of energy security. As China's demand for coal and grain continues to increase, so does the overlap area of their production bases. Unrestrained underground mining can cause serious damage to cropland, leading to increasing conflicts between coal mining and food production. Thus, this paper used a partial backfilling mining technology to control surface subsidence and thus protect cropland. The key to successfully implementing the technology is how to design the panel size. However, the design efficiency of the conventional enumeration method is low. Therefore, this paper proposed a design approach based on improved particle swarm optimization. The results indicated that the approach could quickly find the optimal size of the panel compared with the enumeration method and particle swarm optimization. Moreover, if the longwall panel is mined according to the size designed by the approach, the cropland will be protected, and the cost will be reduced. This study can provide technical support for the cooperative development of cropland protection and coal mining in a coal-cropland overlapping area.

The effect of an additional application of sealer prior to backfilling in the Continuous Wave of Condensation technique.

An additional sealer application was investigated prior to backfilling with the Continuous Wave of Condensation (CWC). 105 Palatal roots were sectioned and prepared to a file size 40, 0.06 taper with Vortex Blue® files. Groups A, B and C had a single sealer application before while groups D, E and F, received a second application of dyed sealer prior to backfilling. Roots were sectioned at 2,3,4,6,7 and 8 mm from the root apex. The percentage of sealer and dentinal tubular penetration depth was calculated at each level. At each ascending level, the sealer percentage decreased for each experimental group while the number of outer third penetration depths increased when all groups were combined. An additional sealer application prior to backfilling had minimal effect on the percentage of sealer or outer third penetration depths and can be considered a clinical preference rather than an imperative step with the CWC technique.