Cement Surface Research Articles

Bond strength of resin-based restorative materials to fast-setting calcium silicate cement using different resin adhesive systems.

This study assessed the bond strength of resin-based restorative materials to fast-setting calcium silicate cement (Aarhus Uinversity, Denmark) when treated with each of two one-bottle universal adhesive systems. The cement surface (N=256) was treated with a self-priming adhesive and a self-etch phosphate monomer-containing adhesive with and without etching of the cement surface. Specimens then received either resin composite or compomer restorative materials (n=32). The bond strength was measured after 1 day and 1500 thermocycles (n=16). The failure type was visually inspected. The cement-adhesive-restorative material interface was visualized using scanning electron microscopy (SEM). The data were analyzed using multiple linear regression. Restorative material type, resin adhesive system, and thermocycling had a statistically significant effect on the bond strength. Compomer restorative material and self-etch universal adhesive system demonstrated statistically significantly higher bond strength values to fast-setting calcium silicate cement, predominantly exhibiting cement cohesive failure. Etching the cement surface enhanced the bond strength of the self-priming universal adhesive. Thermocycling significantly reduced the bond strength. SEM showed self-etch universal adhesive seemingly diffused over the etched cement surface compared to other groups. Self-etch phosphate monomer-containing universal adhesive and compomer resulted in the highest bond strength to fast-setting calcium silicate cement.

The Effect of Human Blood and Platelet-rich Fibrin on the Surface Microhardness of Hydraulic Calcium Silicate-based Cements

Objectives: This study aimed to compare the effect of human blood and platelet-rich fibrin (PRF) on the surface microhardness of hydraulic calcium silicate-based cements (OrthoMTA and RetroMTA). Materials and Methods: Two types of mineral trioxide aggregate, OrthoMTA and RetroMTA, were mixed and placed into cylindrical molds. The lower surfaces of all cements were exposed to saline. The upper surfaces of cements were exposed to human blood, PRF, or phosphate buffer saline (PBS). After storage for 7 days in fully saturated humidity at 37°C, the microhardness of cement surface exposed to blood, PRF, or PBS was measured using the Vickers microhardness test. The data were analyzed using two-way analysis of variance and post hoc Tamhane’s T2 test. The significance level was set at P<0.05. Results: Exposure to blood and PRF significantly decreased the surface microhardness of OrthoMTA and RetroMTA. The microhardness of PBS-contacted cements was significantly higher than that of blood or PRF groups (P<0.001). The microhardness values for OrthoMTA exposed to PRF were significantly higher than the blood group (P=0.020). There were no significant differences between RetroMTA contacted with blood or PRF groups (P=0.985). When exposed to blood or PBS, RetroMTA had a significantly higher microhardness than OrthoMTA (P<0.001 for blood, P=0.002 for PBS). Conclusion: Exposure to blood or PRF decreased the surface microhardness of both cements. Blood-contaminated RetroMTA showed significantly higher surface microhardness than OrthoMTA contacted with blood. No significant difference was found between PRF-contacted OrthoMTA and RetroMTA.

A Copper-Based Coating for the Control of Airborne Viable Bacteria in a Prison Environment

Infections in confined environments can spread by direct contact, contaminated surfaces, and airborne transmission. This is critical in prison facilities, where cleaning and sanitary conditions are inadequate. An alternative is the development of antimicrobial surfaces. A new antimicrobial coating was developed by incorporating copper microparticles into a standard commercial paint, aiming to reduce the concentration of bacteria on surfaces by granting antimicrobial properties to surfaces. The copper additive comprised Cu2Cl(OH)3 deposited on polyhedral zeolite. The efficacy of this coating was evaluated in detention cells in a police station, which are temporary prisons and inherently dirty environments. The experiment compared a cell painted with the copper additive coating and a control cell with the standard paint. Viable coliforms were measured on different surfaces and in the air for five months under normal usage. Bacterial load was reduced by ca. 68% by the copper-amended paint on cement surfaces. Surprisingly, airborne viable coliforms were reduced by ca. 87% in the detention cell treated with the copper coating. This research highlights the potential of antimicrobial coatings in controlling the spread of infections through contact with contaminated surfaces and emphasizes the significant reduction in airborne bacterial load. It is especially relevant for controlling infections where sanitization is limited but can be extended to other built environments, such as healthcare facilities.

The Effect of SiO<sub>2</sub> Addition to the Hydroxyapatite/Curcumin Composite Properties

Hydroxyapatite/curcumin composites have been studied as a calcium phosphate cement candidate. In this research, the effects of adding SiO2 to the hydroxyapatite/curcumin composite on the characteristics of the cement, such as the crystal and surface properties, as well as the release behavior of curcumin in Ringer's solution media, were studied. The composite preparation with and without SiO2 was carried out using a Na2HPO4 2.5% solution. The results showed that the addition of 25% SiO2 to the hydroxyapatite/curcumin composite did not change the crystal properties of hydroxyapatite but produced a more homogenous distribution of the ingredients. The behavior of the composite in Ringer's solution also changes, which is proven by the change in the crystal growth direction and Ca/P ratio. Adding SiO2 produced a composite with a platter and larger particles, as well as a higher Ca/P ratio on the surface. The presence of SiO2 inhibited the release of curcumin in which the ratio of HA: curcumin changed from 77.7%:22.3% to 69.6%:30.4% after 5 d of immersion in Ringer's solution. Thus, besides increasing calcium phosphate deposition on the cement surface, SiO2 also prevents curcumin from being released from the composite.

Removal of Surface Radioactive Uranium(Ⅵ) by Graphene Oxide Modified κ-carrageenan/Konjac Glucomannan Composite Hydrogel

Hydrogel is an effective surface decontamination technology. However, traditional colloid decontaminants face a long curing time and low decontamination rate. A peelable hydrogel coating composed of carrageenan, konjac glucan, and graphene oxide with excellent film-forming performance and decontamination efficiency was explored in this study. The results showed that the graphene oxide was effectively dispersed inside the hydrogel, improving the crosslink density and thermal stability of the hydrogel by forming hydrogen bonds with polysaccharide molecules. The graphene oxide can effectively enhance the decontamination performance of the hydrogel. For stainless steel, ceramic, glass, and rubber surfaces, the decontamination rates of the hydrogel for 30min were 96.95%, 87.6%, 96.27%, and 74.5%, respectively. The decontamination effect was stable to temperature. For cement surfaces, the hydrogel could reach a maximum decontamination rate of 70.68% after 24h. The decontamination efficiency of hydrogel was affected by porosity, surface roughness, and graphene oxide addition. The characterization results of XPS, FT-IR, and SEM/EDS showed that the decontamination process of the composite hydrogel may involve surface wetting, ion diffusion, electrostatic attraction, and physical entanglement.

Effect of pH and hydroxyapatite-like layer formation on the antibacterial properties of borophosphate bioactive glass incorporated poly(methyl methacrylate) bone cement.

Infection is a leading cause of total joint arthroplasty failure. Current preventative measures incorporate antibiotics into the poly (methyl methacrylate) (PMMA) bone cement that anchors the implant into the natural bone. With bacterial resistance to antibiotics on the rise, the development of alternative antibacterial materials is crucial to mitigate infection. Borate bioactive glass, 13-93-B3, has been studied previously for use in orthopedic applications due to its ability to be incorporated into bone cements and other scaffolds, convert into hydroxyapatite (HA)-like layer, and enhance the osseointegration and antibacterial properties of the material. The purpose of this study is to better understand how glass composition and change in surrounding pH effects the composite's antibacterial characteristics by comparing the incorporation of 30% wt/wt 13-93-B3 glass and pH neutral borophosphate bioactive glass into PMMA bone cement. We also aim to elucidate how HA-like layer formation on the cement's surface may affect bacterial adhesion. These studies showed that 13-93-B3 incorporated cements had significant reduction of bacterial growth surrounding the composite beyond 24h of exposure when compared to a neutral borate bioactive glass incorporated cement (p < 0.01) and cement only (p < 0.0001). Additionally, through soaking cement composites in simulated body fluid and then exposing them to a bioluminescent strand of staphylococcus aureus, we found that the presence of a HA-like layer on the 13-93-B3 or pH neutral glass incorporated cement disks resulted in an increase in bacterial attachment on the composite cement's surface, where p < 0.001, and p < 0.05 respectively. Overall, our studies demonstrated that borate bioactive glass incorporated PMMA bone cement has innate antimicrobial properties that make it a promising material to prevent infection in total joint arthroplasties.

Effect of resin cement viscosities and surface roughness on shear bond strength of conditioned polymer infiltrated ceramic network

BackgroundHybrid ceramics bonding with the dentinal substrate is crucial for clinical success and longevity. To enhance adhesion, the surface of ceramic restorations is modified through various conditioning techniques AimEffect of Different Surface Conditioners Erbium-doped yttrium aluminum garnet (ER: YAG) laser and Low-level laser therapy (LLLT) activated Methylene blue (MB) on the surface roughness (Ra) and shear bond strength (SBS) of Polymer infiltrating ceramic network (PICN) discs bonded using different viscosity resin cement before and after thermal aging. Material and MethodsOne hundred and fifty human central incisors and one hundred and fifty-three PICN discs were prepared. PICN discs were randomly allocated into three groups based on the surface conditioning(n = 51) Group 1:10 % HF acid-S, Group 2: LLLT (MB), and Group 3: Er: YAG laser. Following conditioning Ra scores of ten samples were performed. Surface topography of samples was performed using a scanning electron microscope (SEM). Bonding of forty PICN discs from each conditioning group was performed with high (A) or low viscosity (B) dual-curing resin cement (n = 20 each). Each subgroup was divided into two cohorts and subjected to varying storage conditions. The SBS test and failure mode analysis were performed using a universal testing machine and stereomicroscope. Descriptive statistics of SBS and Ra for each group were analyzed using ANOVA and Tukey post hoc tests. HF acid-S attained the highest Ra scores. ResultsGroup 1A (HF-S+HIGH) samples achieved the highest SBS values at baseline. Group 3A, on the other hand, displayed the lowest bond score (Er: YAG laser+HIGH) after thermal aging. Intergroup comparison analysis at baseline unveiled that Group 1A and Group 1B (HF(S) + LOW) displayed no significant difference in their bond strength scores (p>0.05). Following artificial aging, it was observed that Group 2A (LLLT (MB) + HIGH) and Group 3A (Er:YAG laser + HIGH) ) presented comparable SBS(p > 0.05). Thermal aging decreased SBS significantly in all groups. PICN conditioned with HF-S results in high surface roughness. ConclusionPICN conditioned with HF acid with silane and bonded with low-viscosity resin cement to the dentinal substrate is preferable. Aging influences SBS.

Waste-based panels with cement grout as an infill material for composite railway sleepers

The development of high performance and eco-friendly composite railway sleepers at a reasonable price is a great challenge for composite railway sleeper manufacturers. The study proposed a railway sleeper concept based on high-performance fibre composites and low-cost waste-based materials to overcome this challenge. In this concept, thin hollow composite tubes are filled with high volume waste-based panels, which are bonded together with cement grout. This study examined the effect of cement grout, grout thickness, panel types, and surface preparation of the panels on the bond behaviour between the panels and cement grout. It also investigated the bending behaviour of manufactured railway sleepers by evaluating the effects of filling hollow tubes, the orientation of the infill panels, and the types of infill materials. Results indicate that the proposed concept has a high potential for development of high performance and eco-friendly composite railway sleepers at a competitive price due to the incorporation of high volume of waste materials. The results of the study will serve as a guide to the manufacture and design of composite railway sleepers.

Study on the preparation and properties of high-performance foamed cement by multi-factor optimization

The promotion of high-performance foamed cement in engineering is consistent with the objectives of energy conservation and sustainable development. In this work, the effects of the water–binder ratio, foam–grout ratio, mineral powder content and magnesium oxide content on the performance of foamed cement were studied. High-performance foamed cement was prepared considering the above four factors. The results indicated that the pore structure of the foamed cement was effectively modified by adjusting the water–binder and foam–grout ratios, while its compressive strength increased and its setting time decreased when mineral powder and magnesium oxide were added. Pore structure and scanning electron microscopy experiments revealed that the surface of the high-performance foamed cement was covered with many hydration products of mineral powder and magnesium oxide, resulting in a more compact and uniform structure. Simultaneously, these hydration products effectively filled pores with diameters ranging from 0 to 0.2 mm in the high-performance foamed cement, refining its pore structure and thereby enhancing its waterproof performance and drywet cycling stability. Compared with those of commercial foamed cement, the setting time of the high-performance foamed cement was 23.48 % shorter, and its compressive strengths at 1 d and 7 d were 245.78 % and 178.62 % greater, respectively. Furthermore, the production cost per cubic meter of the high-performance foamed cement was 107.29 RMB less than that of ordinary cement. In brief, the high-performance foamed cement can be widely used in a variety of engineering applications because of its performance and economic benefits.

Identification of microRNAs expressed in an animal model of periodontal disease and their impact on pathological processes

MicroRNAs represent a class of small RNAs that act to silence genes post-transcriptionally by inhibiting the translation of target messenger RNAs, and this study aimed to understand how miRNAs influence the set-up of periodontal disease. Periodontitis was induced by inserting a ligature into the left first mandibular molar in a rat model, which was kept for the entire 56 days-time of experiment. After 56 days post-periodontitis induction, the histopathological analysis showed an apical extension of the junctional epithelium, with areas of hyperplasia, exocytosis, and a mixed inflammatory infiltrate with a predominance of neutrophils, lymphocytes, and eventual plasma cells in the deeper layers. The cement surface showed areas of irregularity, covered by cementoblasts and irregular surfaces, confirming the set-up of periodontitis. In the sequencing analysis, 26,404 genes were identified, with 132 reaching statistical significance. Among genes with a statistical difference, 18 were found to encode for microRNAs. The identified microRNAs are primarily involved in bone remodeling by acting on fibroblast growth factors, and collagen production. These outcomes demonstrate a signaling role in bone resorption, which is consistent with the histopathological observations that show the installation of inflammation with epithelial migration and the beginning of the repair process, with cementum resorption. The disclosure of how miRNAs may influence the maintaining of periodontal disease will help the development of new dental materials for the prophylaxis and treatment of alveolar bone resorption.

Long-lasting residual efficacy of Actellic®300CS and Icon®10CS on different surfaces against Anopheles stephensi, an invasive malaria vector.

Anopheles stephensi, a malaria-transmitting mosquito species, has developed resistance to various insecticides such as DDT, Dieldrin, Malathion, and synthetic pyrethroids. To combat this issue, the World Health Organization (WHO) suggests using Actellic®300CS and Icon®10CS for Indoor Residual Spraying to tackle pyrethroid-resistant mosquitoes. The aim of this research project was to evaluate the susceptibility of An. stephensi to certain insecticides at the diagnostic concentration + intensity 5x diagnostic concentration (5XDC) assays in Iran and to study the lasting effectiveness of Actellic®300CS and Icon®10CS against this particular malaria vector. This study assessed the susceptibility of An. stephensi populations in southern Iran to various insecticides, including deltamethrin 0.05%, DDT 4%, malathion 5%, bendiocarb 0.1%, a synergist assay with PBO 4% combined with deltamethrin 0.05%, and an intensity assay using 5x the diagnostic concentration of deltamethrin (0.25%) and bendiocarb 0.5%. Laboratory cone bioassay tests were conducted to determine the residual effectiveness of Actellic®300 and Icon®10CS insecticides on different surfaces commonly found in households, such as cement, mud, plaster, and wood. The tests were carried out following the WHO test kits and standard testing protocols. The An. stephensi populations in Bandar Abbas were found to be susceptible to malathion 5% and deltamethrin 0.25% (5XDC), but exhibited resistance to DDT, standard concentration of deltamethrin, and both standard and intensity concentrations of bendiocarb. In laboratory cone bioassay tests, An. stephensi mortality rates when exposed to Actellic®300CS and Icon®10CS on different surfaces remained consistently more than 80%. Actellic®300CS achieved more than 80% mortality on all substrates for the entire 300-day post-spraying period. Conversely, Icon®10CS maintained mortality rates more than 80% on plaster and wood surfaces for 165 days and on mud and cement surfaces for 270 days post-spraying. Both Actellic®300CS and Icon®10CS demonstrated 100% mortality within 72 h of each test on all surfaces throughout the entire 300-day post-spraying period. The study shows the varying levels of resistance of An. stephensi Bandar Abbas population to different insecticides and demonstrates the consistent performance of Actellic®300CS in controlling these mosquitoes on various surfaces. The findings suggest that long-lasting CS formulations may be more effective for malaria vector control compared to the current options. Further research is needed to validate these findings in field settings and assess the impact of these insecticides on malaria transmission.

(Kesan Rawatan Permukaan pada Ikatan Struktur Mikro antara Muka Zirkonia-Dentin terhadap Saiz Zarah Serbuk Zirkonia yang Berbeza)

Zirconia-based materials have emerged as promising resources for dental restoration applications owing to their excellent strength and aesthetic appearance. In clinical practices, surface treatment on zirconia is essential to ensure enhanced dental bonding. In this study, a novel method was used to produce zirconia block, and the influence of surface treatment on zirconia-dentine microstructure bonding interface was investigated for different particle sizes of zirconia powder. The particle sizes used in this study were 90 and 30 nm on the basis of manufacturer claims. A zirconia block of both particle sizes underwent surface treatment airborne-particle abrasion (50 μm, 0.4 MPa). Dentine specimens were prepared from extracted premolars stored in 0.1% tymol solution before being randomly cemented with the zirconia block sample by using self-adhesive resin cement (RelyX U2000 Clicker, 3M) and then light polymerised. The results after surface treatment showed higher surface roughness values for 90 and 30 nm at 0.17 and 0.18 μm, respectively, than those of the sample without surface treatment at 0.05 and 0.06 μm, respectively, showing no significant difference between particle sizes. Surface treatment improved the bonding of zirconia because the surface roughness allowed for enhanced interlocking of the cement onto the zirconia surface. However, the unbonded dentine and cement was due to the existence of a smear layer on the dentine surface that prevented the selfadhesive resin cement to work well with the dentine surface. Thus, dentine primer must be used to chemically remove the layer and allow for proper bonding between the resin cement and dentine surface.

Estimation of Time-Since-Deposition of bloodstains on different surfaces using ATR-FTIR Spectroscopy and Chemometrics.

Blood is commonly discovered at crime scenes in various forms, including stains, dried residue, pools, and fingerprints on assorted surfaces. Estimating the age of bloodstains is a crucial aspect of reconstructing crime scenes. This research aimed to investigate how the nature of different surfaces affects the estimation of bloodstain age, utilizing a reliable and non-destructive approach. The study employed ATR-FTIR spectroscopy in conjunction with Chemometric techniques such as PCA (Principal Component Analysis) and OPLSR (Orthogonal Signal Correction Partial Least Square Regression Analysis) to analyze spectral data and develop regression models for estimating bloodstain age on cement, metal, and wooden surfaces for up to eleven days. The chemometric models for bloodstains on all three substrates demonstrated strong performance, with predictive Root Mean Square Error (RMSE) values ranging from 1.1 to 1.43 and R2 values from 0.84 to 0.89. Notably, the model developed for metal surfaces was found to be the most accurate with minimal prediction error. The findings of the study showed that the porosity of the substrates upon which bloodstains were found had a discernible influence on the age-related transformations observed in bloodstains; the majority of which occured within the spectral range of 2800cm- 1 to 3500cm- 1.

Numerical modeling and simulation of microbially induced calcite precipitation on a cement surface at the pore scale

Accurate estimation of contaminant transport in cementitious material using numerical tools plays a key role in the risk assessments of nuclear waste disposal. At the pore scale, the increase of microbial activity, such as microbially induced calcite precipitation on cementitious material, causes changes in solid surface topography, pore network geometry, and pore water chemistry, which affect contaminant transport at the core scale and beyond. Consequently, a meaningful estimation of contaminant migration in the subsurface requires a pore-scale investigation of the influence of microbial activity on transport processes. In this study, a pore-scale reactive transport model is presented to simulate the physicochemical processes resulting from microbially induced calcite precipitation on a cement surface. Numerical investigations focus on modeling the reactive transport in a two-dimensional flow-through cell. The model results are validated by experimental data showing an increase in pH and a decrease in calcium concentration due to microbially induced calcite precipitation. Our results show heterogeneous calcite precipitation under transport-limited conditions and homogeneous calcite precipitation under reaction-limited conditions, resulting in non-uniform and uniform changes in the material surface topography. Moreover, power spectral density analysis of the surface data demonstrates that microbially induced calcite precipitation affects the surface topography via both general changes over the entire frequency and local modifications in the high-frequency region. The sensitivity studies provide a comprehensive understanding of the evolution of surface topography due to the microbially induced calcite precipitation at the pore scale, thus contributing to an improved predictability of contaminant transport at the core scale and beyond.

Evaluation of baghdadite (Ca3ZrSi2O9) cements for the application as novel endodontic filling materials

ObjectivesBaghdadite (Ca3ZrSi2O9) cements of various composition have been investigated in this study regarding an application as endodontic filling materials. MethodsCements were either obtained by mixing mechanically activated baghdadite powder with water (maBag) or by subsequently substituting the ß-tricalcium phosphate (ß-TCP) component in a brushite forming calcium phosphate cement. The cements were analyzed for their mechanical performance, injectability, radiopacity, phase composition and antimicrobial properties. ResultsThe cements demonstrated sufficient mechanical performance with a compressive strength of ∼1 MPa (maBag) and 2.3 – 17.4 MPa (substituted calcium phosphate cement), good injectability > 80 % depending on the powder to liquid ratio and an intrinsic radiopacity of 1.13 – 2.05 mm aluminum equivalent. Immersion in artificial saliva proved their bioactivity by the formation of calcium phosphate and calcium silicate precipitates on the cement surface. The bacterial activity of Staphylococcus aureus cultured on the surface of the cements was found to be similar compared to clinical standard ProRoot MTA cement or even reduced by a factor of 3 for Streptococcus mutans. SignificanceIn combination with their antibacterial properties, baghdadite cements are thought to have the potential to fulfil the clinical requirements for endodontic filling materials.

Interlayer Shear Sliding Behaviors during the Fracture Process of Thick Sandstone Roof and Its Mechanism Leading to Coal Mine Tremors

To explore the causes of mine tremors in coal mines with sandstone roofs, a three-point bending loading experiment was designed for composite sandstone layers, and the fracture and interlayer shear slip characteristics of the composite sandstone layers were studied using optical measurement and acoustic emission techniques. The results show that the bending of the rock layers led to interlayer sliding deformation, while the fracturing greatly promoted interlayer sliding. The maximum interlayer slip accelerations during bending deformation and fracturing were 0.6 mm/s2 and 3.8 mm/s2, respectively. During the fracturing of the rock layers, the proportion of acoustic emission shear fracture events increased with the continuous occurrence of long-lasting and high-amplitude acoustic emission events. The mechanism of mine tremors in thick sandstone roofs is as follows: the increase in the area of the goaf causes rock bending deformation and fracturing, accompanied by interlayer shear slip, fracturing of the sandstone layer, and friction dislocation at the cementation surface of the adjacent sandstone layers, which jointly cause vibration of the roof.

Factors associated with mosquito control among construction workers: A systematic review.

Workers in the construction industry frequently work in construction sites with numerous areas that can potentially accumulate water, such as tanks, wet cement surfaces, or water puddles. These water collection sites become ideal breeding grounds for mosquito infestation, which leads to a higher prevalence of mosquito-borne diseases, especially malaria and dengue among construction workers. Despite that numerous factors have been identified in controlling vector-borne diseases, the specific factors that influence mosquito control at construction sites have yet to be explored. This systematic review aims to determine the factors associated with mosquito control among construction workers. Primarily, articles related to factors associated with mosquito control among construction workers were collected from two different online databases (ScienceDirect and EBSCOhost). Two independent reviewers were assigned to screen the titles and abstracts of the collected data, stored in Microsoft Excel, against the inclusion and exclusion criteria. Afterwards, the quality of the included articles was critically assessed using the Mixed Method Appraisal Tool (MMAT). Of the 171 articles identified, 4 were included in the final review. Based on the thorough evaluation, mosquito-related knowledge, practical mosquito prevention measures, and Larval Source Management (LSM) were identified as vital factors associated with mosquito control among construction workers. The significant association between mosquito-related knowledge and control practices indicates higher knowledge linked to effective practices, particularly among female workers and those who were recently infected with malaria. Concurrently, there were notable challenges regarding sustainable preventive measures and larval control methods in construction settings. Implementing effective mosquito control, including knowledge and practice on mosquito control together with vector control, is highly required to suppress the expanding mosquito population. It is recommended that employers provide continuous mosquito control education and training to their employees and reward them with incentives, while employees should comply with the guidelines set by their employers to ensure successful mosquito control and reduce the spread of mosquito-borne diseases in the construction industry.

Further Investigation of CO2 Quasi-Dry Fracturing in Shale Reservoirs—An Experimental Study

The physical properties of shale reservoirs are typically poor, necessitating the use of fracturing technology for effective development. However, the high clay content prevalent in shale formations poses significant challenges for conventional hydraulic fracturing methods. To address this issue, CO2-based fracturing fluid has been proposed as an alternative to mitigate the damage caused by water-based fracturing fluids. In this paper, the applicability of quasi-dry CO2 fracturing in shale reservoirs is examined from three key perspectives: the viscosity of CO2 fracturing fluid, the fracture characteristics induced by the CO2 fracture fluid, and the potential reservoir damage caused by the fracturing fluid. Firstly, the viscosity of CO2 fracturing fluid was determined by a rheological experiment. Rheological tests revealed that the viscosity of CO2 fracturing fluid was significantly influenced by the water–carbon ratio. Specifically, when the water–carbon ratio was 30:70, the maximum viscosity observed could reach 104 mPa·s. Moreover, increasing reservoir temperature resulted in decreased fracturing fluid viscosity, with a 40 °C temperature rise causing a 20% viscosity reduction. Secondly, matrix permeability tests were conducted to investigate permeability alteration during CO2 fracturing fluid invasion. Due to the weak acidity of CO2-based fracturing fluid, the permeability reduction induced by clay hydration was inhibited, and an increase in permeability was observed after a 3-day duration. However, the matrix permeability tends to decrease as the interaction time is prolonged, which means prolonged soaking time can still cause formation damage. Finally, triaxial fracturing experiments facilitated by a three-axis servo pressure device were conducted. The fracture properties were characterized using computed tomography (CT), and 3D reconstruction of fractured samples was conducted based on the CT data. The results demonstrate that CO2 fracturing fluid effectively activates weak cementation surfaces in the rock, promoting the formation of larger and more complex fractures. Hence, CO2 quasi-dry fracturing technology emerges as a method with significant potential, capable of efficiently stimulating shale reservoirs, although a reasonable soaking time is necessary to maximize hydrocarbon production.

Laboratory evaluation of the contact irritancy of a clothianidin solo formulation vs. clothianidin-deltamethrin mixture formulations for indoor residual spraying against pyrethroid-resistant Anopheles gambiae sensu lato

BackgroundClothianidin-based indoor residual spraying (IRS) formulations have become available for malaria control as either solo formulations of clothianidin or a mixture of clothianidin with the pyrethroid deltamethrin. While both formulations have been successfully used for malaria control, studies investigating the effect of the pyrethroid in IRS mixtures may help improve our understanding for development of future IRS products. It has been speculated that the irritant effect of the pyrethroid in the mixture formulation may result in shorter mosquito contact times with the treated walls potentially leading to a lower impact.MethodsWe compared contact irritancy expressed as the number of mosquito take-offs from cement surfaces treated with an IRS formulation containing clothianidin alone (SumiShield® 50WG) to clothianidin-deltamethrin mixture IRS formulations against pyrethroid-resistant Anopheles gambiae sensu lato under controlled laboratory conditions using a modified version of the World Health Organisation cone bioassay. To control for the pyrethroid, comparison was made with a deltamethrin-only formulation. Both commercial and generic non-commercial mixture formulations of clothianidin and deltamethrin were tested.ResultsThe clothianidin solo formulation did not show significant contact irritancy relative to the untreated control (3.5 take-offs vs. 3.1 take-offs, p = 0.614) while all deltamethrin-containing IRS induced significant irritant effects. The number of take-offs compared to the clothianidin solo formulation (3.5) was significantly higher with the commercial clothianidin-deltamethrin mixture (6.1, p = 0.001), generic clothianidin-deltamethrin mixture (7.0, p < 0.001), and deltamethrin-only (8.2, p < 0.001) formulations. The commercial clothianidin-deltamethrin mixture induced similar contact irritancy as the generic clothianidin-deltamethrin mixture (6.1 take-offs vs. 7.0 take-offs, p = 0.263) and deltamethrin-only IRS (6.1 take-offs vs. 8.2, p = 0.071), showing that the irritant effect in the mixture was attributable to its deltamethrin component.ConclusionsThis study provides evidence that the enhanced contact irritancy of the pyrethroid in clothianidin-deltamethrin IRS mixtures can shorten mosquito contact times with treated walls compared to the clothianidin solo formulation. Further trials are needed to directly compare the efficacy of these formulation types under field conditions and establish the impact of this enhanced contact irritancy on the performance of IRS mixture formulations containing pyrethroids.Graphical

Preclinical Evaluation of Bioactive Small Intestinal Submucosa-PMMA Bone Cement for Vertebral Augmentation.

In vertebroplasty and kyphoplasty, bioinert poly(methyl methacrylate) (PMMA) bone cement is a conventional filler employed for quick stabilization of osteoporotic vertebral compression fractures (OVCFs). However, because of the poor osteointegration, excessive stiffness, and high curing temperature of PMMA, the implant loosens, the adjacent vertebrae refracture, and thermal necrosis of the surrounding tissue occurs frequently. This investigation addressed these issues by incorporating the small intestinal submucosa (SIS) into PMMA (SIS-PMMA). In vitro analyses revealed that this new SIS-PMMA bone cement had improved porous structure, as well as reduced compressive modulus and polymerization temperature compared with the original PMMA. Furthermore, the handling properties of SIS-PMMA bone cement were not significantly different from PMMA. The in vitro effect of PMMA and SIS-PMMA was investigated on MC3T3-E1 cells via the Transwell insert model to mimic the clinical condition or directly by culturing cells on the bone cement samples. The results indicated that SIS addition substantially enhanced the proliferation and osteogenic differentiation of MC3T3-E1 cells. Additionally, the bone cement's biomechanical properties were also assessed in a decalcified goat vertebrae model with a compression fracture, which indicated the SIS-PMMA had markedly increased compressive strength than PMMA. Furthermore, it was proved that the novel bone cement had good biosafety and efficacy based on the International Standards and guidelines. After 12 weeks of implantation, SIS-PMMA indicated significantly more osteointegration and new bone formation ability than PMMA. In addition, vertebral bodies with cement were also extracted for the uniaxial compression test, and it was revealed that compared with the PMMA-implanted vertebrae, the SIS-PMMA-implanted vertebrae had greatly enhanced maximum strength. Overall, these findings indicate the potential of SIS to induce efficient fixation between the modified cement surface and the host bone, thereby providing evidence that the SIS-PMMA bone cement is a promising filler for clinical vertebral augmentation.