Formation Damage Research Articles

Formation processes and mechanisms of a fault-controlled colluvial landslide in the Qinling-Daba Mountains, China

Faults play a crucial role in shaping the formation and damage patterns of landslides in the mountainous region, particularly in Qinling-Daba (Qinba) area in China. On 6 October 2022, following a 4-day rainfall event totaling 221.5 mm, a landslide occurred in Hanwang Town, Shaanxi Province. The left boundary of the landslide coincided with a fault, which influence the formation and movement development of the landslide. To further understand and quantified the formation process and damage mechanism of the landslide, a comprehensive study was conducted, incorporating field investigations, local rainfall data, and various methods including unmanned aerial vehicles (UAVs), numerical simulations, and laboratory test. The results indicate that fault dictate the formation of the Lijiaping landslide by influencing the mechanical strength of the rock mass and the catchment topography in the landslide area. Due to fault, the rock mass in the landslide area is high fragmentation, with a softening coefficient of about 0.52. Weathering resulted in numerous residual and slope sediments in the landslide area, providing ample material for the landslide. Meanwhile, the fault activity led to a wedge-shaped topography in the landslide area, with an average Terrain Wetness Index (TWI) of 3.43, significantly higher than the Hanwang Township average of 1.47. This creates a hydrogeological structure favorable for landslides. Numerical simulations revealed that the maximum velocity of the landslide reached 5.05 m/s and the maximum displacement was 53.18 m, both occurring in the central part of the landslide. These findings offer crucial scientific insights for understanding and preventing similar geological hazards.

Mitigation of Fracturing Fluid Leak-Off and Subsequent Formation Damage Caused by Coal Fine Invasion in Fractures: An Experimental Study

During the hydraulic fracturing process of coalbed methane (CBM) reservoirs, significant amounts of secondary coal fines are generated due to proppant grinding and crack propagation, which migrate with the fracturing fluid into surrounding fracture systems. To investigate whether coal fines can form plugs to reduce fluid leak-off during the hydraulic fracturing stage, we conducted physical simulation experiments on coal seam plugging and unplugging to demonstrate that coal fines indeed contribute to reducing fluid leak-off during hydraulic fracturing. We also explored the plugging mechanisms of coal fines under different concentrations and particle sizes in fracturing fluids, and revealed the damage law of coal fines of temporary plugging on reservoir permeability. Research results indicate the leak-off volume of fracturing fluids containing coal fines is lower than an order without coal fines, demonstrating a significant effect of coal fines in decreasing fluid leak-off. The temporary plugging rate of coal fines increases with higher concentrations and decreases with larger particle sizes, achieving rates exceeding 90%. The high temporary plugging effect of coal fines results from the superposition of internal and external filter cakes. Under conditions of small particle size and high concentration, the damage to fractures during the fine return process is minimized. Considering the potential damage of coal fines to propping fractures and wellbore, the concentration of coal fines in fracturing fluids should be kept relatively low while ensuring a high temporary plugging effect. Overall, these findings provide crucial insights into optimizing the temporary plugging performance of coal fines during the hydraulic fracturing stage and controlling their behavior during the fracturing fluid flow-back stage, thereby enhancing reservoir fracturing effectiveness and improving CBM production rates.

SIMPLIFIED COMPUTATIONAL TOOL FOR PREDICTING FORMATION DAMAGE IN OIL WELLS

The present study underscores the significance of regular well test analysis to ensure the accuracy and consistency of data pertaining to the permeability and skin of exploratory wells. This study advances the development of a novel computer model, ASPIRE, which predicts formation damage in oil wells by analysing well-test data. In this context, identifying blocked pore throats in the formation close to the wellbore by paraffinic deposits (scales) and its influence on permeability necessitates routine well-test analysis. The software employs a modified linear regression model developed in this study to perfectly fit the well-test data's infinitely acting linear flow (IARF) region to a straight line. The cases "CASE 1" and "CASE 2" were considered for constant rate transient drawdown well test analyses. The findings indicate that Case 1, with a high skin factor, requires remedial action, such as stimulation, to increase the formation's permeability close to the wellbore for enhanced productivity. In contrast, Case 2 has higher permeability and lower skin factor than Case 1, so stimulation is not required. In addition, R-squared analyses were conducted to validate the results obtained from the developed tool. The analyses reveal an R-square value of 1 for all cases, indicating a 100% accuracy. Therefore, the study concludes that the developed tool is instrumental in accurately predicting formation damage in oil wells.

Masks As a New Hotspot for Antibiotic Resistance Gene Spread: Reveal the Contribution of Atmospheric Pollutants and Potential Risks.

The consumption of disposable surgical masks (DSMs) considerably increased during the coronavirus pandemic in 2019. Herein, we explored the spread of antibiotic resistance genes (ARGs) and the potential risks of antibiotic resistant bacteria (ARB) on DSMs. At environmentally relevant concentrations, the conjugate transfer frequency (CTF) of ARGs increased by 1.34-2.37 folds by 20 μg/m3 of atmospheric water-soluble inorganic ions (WSIIs), and it increased by 2.62-2.86 folds by 80 ng/m3 of polycyclic aromatic hydrocarbons (PAHs). Total suspended particulates (TSP) further promoted the CTF in combination with WSIIs or PAHs. Under WSII and PAH exposure, gene expression levels related to oxidative stress, cell membrane, and the adenosine triphosphate (ATP) were upregulated. WSIIs predominantly induced cellular contact, while PAHs triggered ATP formation and membrane damage. Molecular dynamics simulations showed that WSIIs and PAHs reduced membrane lipid fluidity and increased membrane permeability through interactions with the phosphatidylcholine bilayer. DSM filtering performance decreased, and the CTF of ARGs increased with the wearing time. The gut simulator test showed that ARB disrupted the human gut microbial community and increased total ARG abundance but did not change the ARG abundance carried by ARB themselves. A mathematical model showed that long-term WSII and PAH exposure accelerated ARG dissemination in DSMs.

Distributed fiber optic temperature and strain sensing in cementing and water injection: Insights to well integrity monitoring and multisensing optical fiber cable design

In this study, we installed two fiber optic cables with different designs into a new well, a soft-flat cable and a stainless-steel cable, for distributed fiber optic sensing in cementing and water injection. The two fiber cables were cemented behind casing and the soft-flat cable was used for temperature sensing in cementing as well as cement curing period. The high-speed Rayleigh scanning successfully visualized the cement front tracking from the combined effects of temperature and pressure changes by cement pumping. The temperature variations in cement curing reveled the cement volume and have the potential to identify defects in annular cement and formation damage caused by cementing. The water injection test for strain sensing was carried out with increasing injection rate from 100 L/min to 200 L/min. Strain profiles from the two fiber cables suggested that the strain responses reveal alternation of sand and silt, and reservoir heterogeneity. The water injection results showed that the measured strains of the two cables matched fairly well and the stainless-steel cable showed a high strain sensitivity responding to injection pressure (1 με/5 kPa). Comparison of strain measurement results of the two cables provided valuable insights for future strain fiber cable design. Strain sensing results also indicated a high capability to capture small pressure changes in the heterogeneous layers. Thus, our results demonstrate the high potential of using strain sensing for leak detection and well integrity monitoring in fluid injections, particularly for the long-term monitoring at CO2 storage site.

Investigation of genotoxicity induced by intermediate frequency magnetic field combined with ionizing radiation: In vitro study on human fibroblast cells

These days, exposure to electromagnetic fields has become omnipresent in modern society. Not only the extremely-low frequency and radiofrequency, but also intermediate frequency (IF) magnetic field (MF) might be absorbed in the human body resulting in an ever-growing concern about their possible health effects. Devices, such as induction cooktops, chargers, compact fluorescent lamps, touchscreens and electric vehicles emit a wide range of intermediate frequency fields. We investigated the effects of 22 kHz or 250 kHz intermediate frequency magnetic field exposure on the human skin cells. We also examined the adaptive response phenomenon; whether IF MF exposure could possibly reduce the harmful genotoxic effects of ionizing radiation. To get answers to these questions, in vitro studies were carried out on fibroblast cells to investigate the effects on oxidative stress, DNA damage and micronucleus formation. We found a decreased micronucleus formation due to the 22 kHz IF MF exposure and significantly increased oxidative stress in fibroblast cells, which were exposed only to 250 kHz IF MF. We were unable to detect the protective or co-genotoxic effects of intermediate frequency magnetic field exposure combined with ionizing radiation, thus we found no evidence for the adaptive response phenomena.

DNA Damage and Repair in PBMCs after Internal Ex Vivo Irradiation with [223Ra]RaCl2 and [177Lu]LuCl3 Mixtures.

The combination of high and low LET radionuclides has been tested in several patient studies to improve treatment response. Radionuclide mixtures can also be released in nuclear power plant accidents or nuclear bomb deployment. This study investigated the DNA damage response and DNA double-strand break (DSB) repair in peripheral blood mononuclear cells (PBMCs) after internal exposure of blood samples of 10 healthy volunteers to either no radiation (baseline) or different radionuclide mixtures of the α- and β-emitters [223Ra]RaCl2 and [177Lu]LuCl3, i.e., 25 mGy/75 mGy, 50 mGy/50 mGy and 75 mGy/25 mGy, respectively. DSB foci and γ-H2AX α-track enumeration directly after 1 h of exposure or after 4 h or 24 h of repair revealed that radiation-induced foci (RIF) and α-track induction in 100 cells was similar for mixed α/β and pure internal α- or β-irradiation, as were the repair rates for all radiation qualities. In contrast, the fraction of unrepaired RIF (Qβ) in PBMCs after mixed α/β-irradiation (50% 223Ra & 50% 177Lu: Qβ = 0.23 ± 0.10) was significantly elevated relative to pure β-irradiation (50 mGy: Qβ, pure = 0.06 ± 0.02), with a similar trend being noted for all mixtures. This α-dose-dependent increase in persistent foci likely relates to the formation of complex DNA damage that remains difficult to repair.

Two Olea europaea L.Extracts Reduce Harmful Effects in a Model of Neurotoxicity: Involvement of the Endoplasmic Reticulum.

Prolonged exposure to lead has been recognized as harmful to human health as it may cause neurotoxic effects including mitochondrial damage, apoptosis, excitotoxicity, and myelin formation alterations, among others. Numerous data have shown that consuming olive oil and its valuable components could reduce neurotoxicity and degenerative conditions. Olive oil is traditionally obtained from olive trees; this plant (Olea europaea L.) is an evergreen fruit tree.In this manuscript, two extracts have been used and compared: the extract from the leaves of Olea europaea L. (OE) and the extract derived from OE but with a further sonication process (s-OE). Therefore, the objectives of this experimental work were as follows: 1) to generate an innovative extract; 2) to test both extracts on a model of neurotoxicity of human neurons induced following lead exposure; and 3) to study the mechanisms behind lead-induced neurotoxicity.The results showed that the mechanism involved in the neurotoxicity of lead included dysfunction of the cellular endoplasmic reticulum, which suffered oxidative damage. In addition, in all experiments, s-OE was more effective than OE, having greater and better effects against lead-induced damage and being dissolved in a smaller amount of EtOH, which promotes its sustainability.

Transplantation of miR-145a-5p modified M2 type microglia promotes the tissue repair of spinal cord injury in mice

BackgroundThe traumatic spinal cord injury (SCI) can cause immediate multi-faceted function loss or paralysis. Microglia, as one of tissue resident macrophages, has been reported to play a critical role in regulating inflammation response during SCI processes. And transplantation with M2 microglia into SCI mice promotes recovery of motor function. However, the M2 microglia can be easily re-educated and changed their phenotype due to the stimuli of tissue microenvironment. This study aimed to find a way to maintain the function of M2 microglia, which could exert an anti-inflammatory and pro-repair role, and further promote the repair of spinal cord injury.MethodsTo establish a standard murine spinal cord clip compression model using Dumont tying forceps. Using FACS, to sort microglia from C57BL/6 mice or CX3CR1GFP mice, and further culture them in vitro with different macrophage polarized medium. Also, to isolate primary microglia using density gradient centrifugation with the neonatal mice. To transfect miR-145a-5p into M2 microglia by Lipofectamine2000, and inject miR-145a-5p modified M2 microglia into the lesion sites of spinal cord for cell transplanted therapy. To evaluate the recovery of motor function in SCI mice through behavior analysis, immunofluorescence or histochemistry staining, Western blot and qRT-PCR detection. Application of reporter assay and molecular biology experiments to reveal the mechanism of miR-145a-5p modified M2 microglia therapy on SCI mice.ResultsWith in vitro experiments, we found that miR-145a-5p was highly expressed in M2 microglia, and miR-145a-5p overexpression could suppress M1 while promote M2 microglia polarization. And then delivery of miR-145a-5p overexpressed M2 microglia into the injured spinal cord area significantly accelerated locomotive recovery as well as prevented glia scar formation and neuron damage in mice, which was even better than M2 microglia transplantation. Further mechanisms showed that overexpressed miR-145a-5p in microglia inhibited the inflammatory response and maintained M2 macrophage phenotype by targeting TLR4/NF-κB signaling.ConclusionsThese findings indicate that transplantation of miR-145a-5p modified M2 microglia has more therapeutic potential for SCI than M2 microglia transplantation from epigenetic perspective.Graphical

Genomic diversity, antibiotic resistance, and virulence in South African Enterococcus faecalis and Enterococcus lactis isolates

This study presents the empirical findings of an in-depth genomic analysis of Enterococcus faecalis and Enterococcus lactis isolates from South Africa. It offers valuable insights into their genetic characteristics and their significant implications for public health. The study uncovers nuanced variations in the gene content of these isolates, despite their similar GC contents, providing a comprehensive view of the evolutionary diversity within the species. Genomic islands are identified, particularly in E. faecalis, emphasizing its propensity for horizontal gene transfer and genetic diversity, especially in terms of antibiotic resistance genes. Pangenome analysis reveals the existence of a core genome, accounting for a modest proportion of the total genes, with 2157 core genes, 1164 shell genes, and 4638 cloud genes out of 7959 genes in 52 South African E. faecalis genomes (2 from this study, 49 south Africa genomes downloaded from NCBI, and E. faecalis reference genome). Detecting large-scale genomic rearrangements, including chromosomal inversions, underscores the dynamic nature of bacterial genomes and their role in generating genetic diversity. The study uncovers an array of antibiotic resistance genes, with trimethoprim, tetracycline, glycopeptide, and multidrug resistance genes prevalent, raising concerns about the effectiveness of antibiotic treatment. Virulence gene profiling unveils a diverse repertoire of factors contributing to pathogenicity, encompassing adhesion, biofilm formation, stress resistance, and tissue damage. These empirical findings provide indispensable insights into these bacteria’s genomic dynamics, antibiotic resistance mechanisms, and virulence potential, underlining the pressing need to address antibiotic resistance and implement robust control measures.

Melatonin intervention to prevent nanomaterial exposure-induced damages: A systematic review and meta-analysis of in vitro and in vivo studies.

Given its antioxidant, anti-inflammatory, and antiapoptotic properties, melatonin (MEL), a health-caring food to improve sleep disorders, is hypothesized to protect against nanomaterial exposure-induced toxicity. However, the conclusion derived from different studies seemed inconsistent. A meta-analysis of all available preclinical studies was performed to examine the effects of MEL on nanomaterial-induced damages. Eighteen relevant studies were retrieved through searching five electronic databases up to December 2023. The meta-analysis showed that relative to control, MEL treatment significantly increased cell viability (standardized mean difference [SMD = 1.27]) and alleviated liver function (lowered AST [SMD = -3.89] and ALT [SMD = -5.89]), bone formation (enhanced BV/TV [SMD = 4.13] and lessened eroded bone surface [SMD = -5.40]), and brain nerve (inhibition of AChE activity [SMD = -3.60]) damages in animals. The protective mechanisms of MEL against damages caused by nanomaterial exposure were associated with its antiapoptotic (decreased Bax/Bcl-2 ratio [SMD = -4.50] and caspase-3 levels [dose <100 μM: SMD = -3.66]), antioxidant (decreased MDA [in vitro: SMD = -2.84; in vivo: SMD = -4.27]), and anti-inflammatory (downregulated TNF-α [in vitro: SMD = -5.41; in vivo: SMD = -3.21] and IL-6 [in vitro: SMD = -5.90; in vivo: SMD = -2.81]) capabilities. In conclusion, our study suggests that MEL should be supplemented to prevent damages in populations exposed to nanomaterials.

Emergency control of dinoflagellate bloom in freshwater with chlorine enhanced by solar radiation: Efficiency and mechanism

Dinoflagellate requires a lower temperature and blooms frequently in the spring and autumn compared to regular cyanobacteria. The outbreak of dinoflagellate bloom will also lead to the death of some aquatic organisms. However, research on freshwater dinoflagellates is still lacking due to the challenges posed by classification and culture in laboratory. The removal effect and mechanism of Peridinium umbonatum (P. umbonatum, a typical dinoflagellate) were investigated using solar/chlorine in this study. The effect of simulated solar alone on the removal of algae was negligible, and chlorine alone had only a slight effect in removing algae. However, solar/chlorine showed a better removal efficiency with shoulder length reduction factor and kmax enhancement factor of 2.80 and 3.8, respectively, indicating a shorter latency period and faster inactivation rate for solar/chlorine compared to solar and chlorine alone. The removal efficiency of algae gradually increased with the chlorine dosage, but it dropped as the cell density grew. When the experimental temperature was raised to 30 °C, algal removal efficiency significantly increased, as the temperature was unsuitable for the survival of P. umbonatum. Attacks on cell membranes by chlorine and hydroxyl radicals (•OH) produced by solar/chlorine led to a decrease in cell membrane integrity, leading to a rise in intracellular reactive oxygen species and an inhibition of photosynthetic and antioxidant systems. Cell regeneration was not observed in either the chlorine or solar/chlorine systems due to severe cell damage or cysts formation. In addition, natural solar radiation was demonstrated to have the same enhancing effect as simulated solar radiation. However, the algal removal efficiency of solar/chlorine in real water was reduced compared to 119 medium, mainly due to background material in the real water substrate that consumed the oxidant or acted as shading agents.

Влияние кормовой пробиотической добавки «Ветоспорин-Ж» (Bacillus subtilis) и минеральной добавки «Цеолит» (опока) на проявление генотоксических эффектов в клетках крови молоди стерляди (Acipenser ruthenus) в условиях аквакультуры

In modern conditions of declining natural sturgeon populations in the Volga-Caspian basin, the role and importance of aquaculture is increasing. In the Astrakhan region, due to the presence of a large natural water fund, cage farming of fish, including sterlet, is widely developed. Cage farming of sturgeon in natural water bodies is associated with the impact of anthropogenic pollution, in this area it is associated with water pollution in the river delta Volga, and the deterioration of the hydrochemical regime, which directly affects fish farming. One of the factors of the negative impact of these changes in the aquatic environment is genotoxicity, the degree of manifestation of which can be assessed using accessible and modern methods, which include micronuclear and DNA comet tests. A serious consequence of the genotoxic effect of pollution is the formation of damage to the DNA of the fish body. The purpose of this work was to assess the frequency of appearance of micronuclei and the degree of DNA damage in the blood cells of juvenile sterlet, as well as the selection of functional additives in food that will reduce the effects of genotoxic pressure from a natural water source. In a scientific laboratory, a series of experiments was carried out on feeding juvenile sterlet delivered from a fish farm in the Volga delta. All juvenile sterlet, both at the beginning and at the end of the experiment, were characterized by a normal physiological state, low levels of DNA comets, and the number of erythrocytes with micronuclei was slightly higher than normal. As a result of experimental feeding, reliable data were obtained that food with the addition of the probiotic drug “Vetosporin-Zh” based on the bacteria Bacillus subtilis contributed to a significant increase in weight gain and body length. All analyzed indicators of DNA comets were significantly lower in the group that was fed with the introduction of a probiotic (the micronucleus test turned out to be less sensitive in this case). The mineral additive “Zeolite” did not show such effectiveness. Thus, the addition of Bacillus subtilis-based preparations when feeding juvenile sturgeon can be reasonably recommended to effectively reduce genotoxic stress for fish, mainly to reduce DNA damage.

Machining damage in the fabrication of polycrystalline diamond micro end mill with laser and grinding combined processing method

The high hardness and wear resistance of polycrystalline diamond (PCD) micro tool make it widely used in precision machining of small parts of difficult-to-machine materials. The laser and grinding combined machining is an effective method to fabricate PCD micro tools, but the machining damage is difficult to control, which will reduce the cutting performance and tool life. Therefore, this paper aims to deeply study the damage forms and damage formation mechanisms during the fabrication process of PCD micro end mills, so as to improve the quality of the PCD micro mills. The laser and grinding combined machining experiments of PCD micro end mill are carried out, and the surface morphology characteristics and cutting edge of the mill are observed and analyzed. The influence of process parameters on the fabrication quality of PCD micro mill is investigated. The experimental results show that the high temperature of the laser is the main factor causing damage, which causes the melting and oxidation of the surface material, and further forms micro cracks, pits and oxidized attachments on the PCD mill. In addition, diamond phase transformation and excessive removal of cobalt-rich layer will also lead to graphitization and micro-grooves on the mill surface. For the grinding process, the cutting edge is fractured by the impact of the wheel, resulting in micro notches, micro pits and micro cracks. The intergranular crack expansion of PCD material and cleavage breakage of diamond particles are the main causes of micro cracks and micro pits on the mill surface. In addition, the chips will also scratch the tool surface to produce micro nicks and cause the chips coating on the rake face. The research results are helpful to further understand the damage mechanism of laser and grinding combined machining PCD mill, so as to improve the fabrication quality of micro tools.

Evaluation of formation damage and filter cake removal with a new LPM drilling fluid additive

This study evaluates the LPM-FBR drilling fluid additive's performance in minimizing formation damage and facilitating filter cake removal in fractured and high-permeability cores. Using a Formation Damage System Apparatus, two experimental studies were conducted to address the challenge of balancing fluid loss control and formation damage mitigation in fractured reservoirs. The first study, comparing a base saltwater mud with and without LPM-FBR on a 1231 mD fractured sandstone core, showed that LPM-FBR significantly enhanced fluid loss control. It withstood 552 psi overbalance pressure with minimal fluid loss (85.6 mL over 6 h), effectively sealing fractures. However, it reduced return permeability from 1500 to 47.8 mD. The second study, using a 2000 mD fractured core, demonstrated LPM-FBR's effectiveness in limiting filtrate invasion to 5.7 mL over 4 h at 600 psi overbalance. Subsequent cleaning with caustic soda proved ineffective, severely impairing return permeability to 19–28 mD. A breaker solution with a high flow rate of water flushing showed more promise in filter cake removal. This research highlights the trade-offs between fluid loss control and formation damage when using LPM-FBR muds. While excelling in minimizing fluid losses under high overbalance conditions, the additive poses challenges in post-drilling permeability restoration. These findings underscore the need for comprehensive removal procedures to mitigate long-term productivity impairment in fractured reservoirs, contributing valuable insights for optimizing drilling fluid design and post-drilling cleanup strategies.

Fabrication of a hydrogel reinforced with titanium nanoparticles to reduce fine migration and remediation of formation damage during low-salinity waterflooding

A hydrogel nanocomposite was formulated and synthesized to control fine migration. The hydrogel was reinforced with titanium nanoparticles and its performance was studied. SEM and TEM images confirmed the formation of a homogeneous structure with uniform nanoparticle dispersion as fillers. Nanoparticles added to a hydrogel structure created a 3D structure with shear-thinning properties and a 92% increase in maximum elastic modulus. The hydrogel nanocomposite exhibited viscoelastic characteristics that endured temperature changes up to 200 °C and a delay in thermal degradation from 93 °C to 213 °C. Nanoparticles also reduced the sensitivity factor to salinity. Optimal flooding composition involves a pH of 5.4, a salinity of 10,000 ppm, and a 4.98% nanocomposite concentration. Waterflooding under these conditions reduces fine migration by 62%. The synthesized nanocomposite hydrogel can increase the contact angle of oil with rock by 77°, this remarkable property, coupled with its superior thermal stability, strong rheological strength, and low operational risk, positions this novel chemical as an outstanding solution for fine migration control in harsh reservoir environments without causing formation damage. So the hydrogel nanocomposite, by effectively preventing fine migration and production, safeguards reservoir integrity and extends its production lifespan, ensuring a sustainable approach to resource utilization and a reliable energy supply for future generations.

Specificity of DNA damage formation induced by femtosecond near-infrared laser filamentation in water

We investigated the deoxyribonucleic acid (DNA) damage induced by laser filamentation, which was generated by focusing femtosecond near-infrared Ti:Sapphire laser light in water at several repetition rates ranging from 1000 Hz to 10 Hz. Using plasmid DNA (pUC19), the single-strand break, double-strand break, nucleobase lesions, and the fragmented DNA were analyzed and quantified by agarose gel electrophoresis. Additionally, the H2O2 concentration after irradiation was determined. We observed that (1) the DNA damage per laser shot and (2) the enzyme-sensitive base lesions per total DNA damage decreased as the laser repetition rate increased. Furthermore, (3) extraordinarily short DNA fragments were likely to be produced, compared with those produced using X-rays, and (4) most OH radicals could be eliminated by recombination to generate H2O2, preventing them from damaging the DNA. The Monte-Carlo simulation of the strand break formation implies that the observed dependency of strand break efficiency on the laser repetition rate is mainly due to diffusion of DNA molecules. These findings quantitatively and qualitatively revealed that an intense laser pulse induces a specific DNA damage profile that is not induced by X-rays, a sparsely ionizing radiation source.

Temporal and Dosage Impact of Magnesium Oxide Nanoparticles on Grass Carp: Unveiling Oxidative Stress, DNA Damage and Antioxidant Suppression

Magnesium oxide nanoparticles (MgO NPs) have gained significant importance in biomedicine and variety of nanotechnology-based materials used in the agriculture and biomedical industries. However, the release of different nanowastes in the water ecosystem becomes a serious concern. Therefore, this study was executed to evaluate the toxic impacts of MgO NPs on grass carp. A total of 60 grass carp were randomly divided in three groups (G0, G1, and G2). Fish reared in group G0 were kept as control while fish of groups G1 and G2 were exposed to 0.5mg/L and 0.7mg/L MgO NPs respectively, mixed in water for 21 days. The 96h median lethal concentration (LC50) of MgO NPs was found to be 4.5mg/L. Evaluation of oxidative stress biomarkers, antioxidant enzymes, DNA damage in different visceral organs and the presence of micronuclei in erythrocytes were determined on days-7, 14, and 21 of the trial. Results revealed a dose and time-dependent significantly increased values of reactive oxygen species, lipid peroxidation product, DNA damage in multiple visceral organs and formation of micronuclei in the erythrocytes of treated fish (0.7mg/L). The results on antioxidant profile exhibited significantly lower amounts of total proteins, catalase, superoxide dismutase and peroxidase in visceral organs of the fish exposed to MgO NPs (0.5 and 0.7mg/L) at day 21 of trial compared to control group. In conclusion, it has been recorded that MgO NPs severely influence the normal physiological functions of the grass carp even at low doses.

The interplay of DNA damage and repair, gene expression, and mutagenesis in mammalian cells during oxidative stress.

We investigated the interplay among oxidative DNA damage and repair, expression of genes encoding major base excision repair (BER) enzymes and bypass DNA polymerases, and mutagenesis in mammalian cells. Primary mouse embryonic fibroblasts were challenged with oxidative stress induced by methylene blue plus visible light, and formation and repair of DNA damage, changes in gene expression, and mutagenesis were determined at increasing intervals post-treatment (0 - 192 hours). Significant formation of oxidative DNA damage together with upregulation of Ogg1, Polβ, and Polκ, and no changes in Mutyh and Nudt1 expression were found in treated cells. There was a distinct interconnection between Ogg1 and Polβ expression and DNA damage formation and repair whereby changes in expression of these two genes were proportionate to the levels of oxidative DNA damage, once a 3-plus hour lag time passed (P < 0.05). Equally notable was the matching pattern of Polκ expression and kinetics of oxidative DNA damage and repair (P < 0.05). The DNA damage and gene expression data were remarkably consistent with mutagenicity data in the treated cells; the induced mutation spectrum is indicative of erroneous bypass of oxidized DNA bases and incorporation of oxidized deoxynucleoside triphosphates during replication of the genomic DNA. Our findings support follow-up functional studies to elucidate how oxidation of DNA bases and the nucleotide pool, overexpression of Polκ, delayed upregulation of Ogg1 and Polβ, and inadequate expression of Nudt1 and Mutyh collectively affect mutagenesis consequent to oxidative stress.

Formation damage management through enhanced drilling efficiency: Mud weight and loss analysis in Asmari Formation, Iran

Drilling fluid loss is one of the key challenges in the drilling operations of oil and gas wells, which has a direct effect on the formation damage and production operations. Hence, it is very important to study mud loss and investigate the factors affecting its locations. In this study, the fluid distribution model and its influencing factors in the Oligo-Miocene Asmari reservoir have been studied. For this purpose, the drilling data, mud loss maps, mud weight, and the condition of mud loss in one field have been analyzed. Additionally, this study aims to provide a more precise understanding of mud loss within the reservoir, as well as examining its correlation with drilling issues. The drilling history of the wells and maps of the mud weight required for drilling the Asmari Formation in different parts of the field were used.The drilling challenges encountered in the examined wells were systematically analyzed, and distribution maps highlighting the prevalence of these issues across various sectors were generated. Also, the density of wells with drilling problems was determined in different parts of the field, and areas with high risk were introduced. The results of this study show that the highest amount of loss, a volume of 120 bbl/h, has been occurred in the main anticline areas of the field (the southeast and northwest areas of the structure), where the highest mud weight of about 130 lb/ft3 was used. Most of the wells with drilling problems are located in this area of the field. Wells situated farther away from this region were drilled with notably reduced risk levels compared to those in closer proximity.