Increasing Exposure Time Research Articles

Effects of general and saturated humidity on concrete performance deterioration under sulfur dioxide attack

A large amount of SO2 is emitted with the rapid development of industrialization, and there are big differences in the deterioration of concrete subjected to SO2 attack between the environments of general humidity and saturated humidity. This paper conducted the simulation tests of concrete subjected to SO2 attack at general humidity (RH = 80 %) and saturated humidity (RH = 98 %), and the sulfuration depth, mass, and compressive strength were comparatively studied. The distributions of pore-solution pH and SO2- 4 concentration of concrete at different exposure times and depths were analyzed, and the deterioration mechanisms on concrete under SO2 attack in these environments were compared. The results indicated that the sulfuration depth and mass remained unchanged in the middle and later periods of the attack at 80 % RH, and the compressive strength at 20d was still larger than that before SO2 attack. However, the sulfuration depth and mass increased rapidly at 98 % RH, and the compressive strength loss rate was 18.80 % at 20d. The ions concentrations at 98 % RH changed greatly with increasing exposure time, and the pH and SO2-4 concentration of concrete at 1 mm at 20d were 2.41 times less and 3.86 times larger than those at 80 % RH, respectively. The initial product at 80 % RH was ettringite, which converted to gypsum with the progress of SO2 attack, and these expansive products decreased the porosity of concrete. A large amount gypsum was produced at 98 % RH, leading to the initiation and propagation of microcracks, and the porosity increased to 41.43 %.

Novel Chromium–Silicon Slurry Coatings for Hot Corrosion Environments

Ni-based superalloys are commonly used in gas turbines because of their exceptional high-temperature mechanical properties. To secure a long service life, the materials must also have sufficient corrosion resistance. Therefore, diffusion coatings are widely used to enrich the surface in protective oxide scale-forming elements. For temperatures between 650 and 950 °C, where hot corrosion occurs, Cr-based coatings are advantageous. These are commonly applied via the laborious pack cementation process. Recently, a novel cost-effective Cr/Si slurry coating process has been developed which demonstrated resistance to oxidative high-temperature environments. Here, the protection of the slurry coatings against hot corrosion type I at 900 °C on the Ni-based superalloy Rene 80 is investigated and compared to coatings produced by pack cementation. Prior to the 300-h exposures in air containing 0.1% SO2 at 900 °C, 4 mg/cm2 of Na2SO4 was deposited on the material surfaces. The uncoated Rene 80 exhibited rapid dissolution of the initial oxide scale followed by catastrophic break away oxidation. In comparison, the slurry coatings showed significantly improved hot corrosion resistance compared to the uncoated alloy and a better protection than a Cr pack cementation coating. The Cr pack cemented Rene 80 showed improved hot corrosion resistance, but Cr depletion in the subsurface zone occurred with increasing exposure time, associated with the propagation of Al internal oxidation and increasing sulfidation. In contrast, the slurry coatings formed an external Cr2O3 scale coupled with an agglomeration of SiO2 underneath and a continuous Al2O3 subscale which offered a better diffusion barrier and leading to superior long-term protection against hot corrosion.

Potential of cold plasma pretreatment for preserving biochemical attributes and ensuring the microbiological safety of saffron stigma.

Saffron, similar to numerous other agricultural commodities, is susceptible to microbial contamination during cultivation and postharvest handling. Cold plasma treatment has emerged as an effective method for microbial inactivation while preserving food quality. The aim of this research was to preserve the color integrity and minimize the presence of microorganisms in dried saffron stigma by implementing cold plasma pre-treatment. Process parameters were optimized using the response surface method (RSM), considering the type of atmosphere (argon and air), plasma exposure time (1, 5, and 10 min), and plasma power (40, 70, and 100 W) as independent variables. The objectives were to maximize crocin content and minimize the total microbial load. The analysis of the response surface revealed that the argon atmosphere had a more significant impact on reducing microbial contamination than air, and an increase in plasma exposure time led to a decrease in microbial load. The maximum reduction in microbial load, by 0.9 logarithmic cycles compared to the control, was achieved with a 10-min treatment at 40 W power. Extended plasma exposure durations led to a minor reduction in the color, taste, aroma, and antioxidant properties of saffron stigma. Specifically, the color, taste, and aroma decreased by 0.5%, 0.5%, and 0.08%, respectively, with longer plasma exposure times. The antioxidant activity decreased by 0.64% with prolonged exposure time. However, the plasma-treated samples did not show any signs of Escherichia coli, mold, or yeast. Furthermore, our findings demonstrated that the type of atmosphere significantly influenced the reduction of infection and maintenance of saffron stigma's color quality. Cold plasma pretreatment holds promise as a viable method for preserving the physicochemical attributes of saffron while effectively reducing microbial contamination.

Manufacturing and corrosion characterization of Ti-10%Zr-2%Sn-8%Mo alloy and Ti-10%Zr-2%Sn-8%Ta alloy after various exposure intervals in chloride solution

Ti-10%Zr-2%Sn-8%Mo alloy and Ti-10%Zr-2%Sn-8%Ta alloy were manufactured using the technique of powder metallurgy. The corrosion of the two alloys was performed after 1 h, 24 h, and 48 h immersion in 3.5% NaCl solution using electrochemical impedance spectroscopy (EIS), cyclic polarization (CPP), and the measurement of current over time. EIS (Nyquist and Bode) data indicated that the Ti-10%Zr-2%Sn-8%Ta alloy has higher polarization resistance compared to the Ti-10%Zr-2%Sn-8%Mo alloy. CPP results revealed that the Ti-10%Zr-2%Sn-8%Ta alloy has higher corrosion resistance and lower corrosion currents. The experiments of measuring the change of current over time at 500 mV showed that both the Ti-10%Zr-2%Sn-8%Mo alloy and the Ti-10%Zr-2%Sn-8%Ta alloy do not show pitting corrosion, which confirms the CPP results. Extending the time to 24 h and 48 h increased the corrosion resistance for both alloys. The surface of the alloys after being corroded in NaCl solution were investigated using scanning electron microscopy and energy dispersive spectroscopy. All investigations confirmed that the Ti-10%Zr-2%Sn-8%Ta alloy is more passivated than the Ti-10%Zr-2%Sn-8%Mo alloy and the increase of exposure time to 48 h enhances the passivation of both alloys, which recommends that these alloys are best choice in the biomedical applications.

Clinical use and applications of a citrate-based antiseptic lavage for the prevention and treatment of PJI.

Total joint arthroplasties (TJA) are some of the most commonly performed surgeries in the United States with the number of TJA expected to rise significantly over the next decade as the population ages and arthritic burden worsens. However, the rise in TJA volume correlates with a heightened risk of complications, notably prosthetic joint infections (PJI), despite their low occurrence rate of less than 2%. PJI imposes a significant burden on surgery success, patient well-being, and healthcare costs, with an estimated annual expense of 1.85 billion dollars for hip and knee PJI by 2030. This manuscript delves into the pathophysiology of PJI, exploring our current understanding of the role of bacterial biofilm formation on implanted foreign hardware, providing protection against the host immune system and antibiotics. The article reviews current agents and their efficacy in treating PJI, as well as their cytotoxicity toward native cells involved in wound healing, prompting the exploration of a novel citrate-based solution. The paper highlights the superior properties and efficacy of a novel citrate-based irrigation solution on the treatment and prevention of PJI via increased antimicrobial properties, greater biofilm disruption, increased exposure time, and reduced cytotoxicity compared to conventional solutions, positioning it as a promising alternative. It also provides a perspective on its clinical use in the operating theater, with a step-by-step approach in TJA, whether primary or revisionary.

Evaluation of Acute Toxicity and Lethal Concentration (LC50) of Cypermethrin (25% EC) in Adults of Cyprinus carpio (Linnaeus 1758)

The present study attempted to determine the acute toxicity and medial lethal concentrations of Cypermethrin (25% EC) for common carp Cyprinus carpio using Finney’s static bioassay (1971), probit analysis method. The LC50 values for 24, 48, 72 and 96 hr were found to be 3.962 µl Lit-1, 3.767 µl Lit-1, 3.349 µl Lit-1 and 2.924 µl Lit-1 respectively. Fish (weight 90–100 g, length up to 18±2 cm) were exposed to different concentrations of cypermethrin which were 1.5 µl Lit-1, 2.0 µl Lit-1, 2.5 µl Lit-1, 3.0 µl Lit-1, 3.5 µl Lit-1, 4.0 µl Lit-1 and 4.5 µl Lit-1 up to 96 hr. LC50 value decreases with an increase in exposure time. During this exposure period, abnormal behaviors like restlessness, hyperactivity, erratic movements, increased opercular movements, and loss of equilibrium and response were noticed in carp. Over secretion of mucous all over the body surface along with respiratory stress and mortality was also observed.

Ensuring quality indicators of photopolymer 3D printing by using mathematical modeling and test models

The subject of the research in the article is the analysis of the influence of technological parameters of photopolymer printing on the appearance of defects in the printing process. Test models for analysis are used, which contain elements that are affected by changes in technological parameters. The purpose of the work is to determine the dependence between the technological parameters of photopolymer printing and the defects that arise because of printing using models for testing. The article addresses the following tasks: analysis of existing test models and determination of model elements and the influence of technological parameters on them. The methods used for the research are mathematical analysis in the form of univariate linear regression and the empirical method. This method consists in comparing and measuring the difference between individual test samples to obtain values that will later be used in regression analysis. The following results were obtained: the dependence of technological factors and their influence on the elements of the test model was determined, which consists in changing the physical dimensions of the test models. With insufficient exposure time, the dimensions of the model are reduced, and defects are created. When the exposure time increases, the dimensions of the model increase linearly, defects appear in the form of holes disappearing or their sizes changing. Conclusions: because of an experimental study, which consists in printing test models and their analysis with the help of linear one-factor regression, the dependence between the exposure time and the physical dimensions of the model was determined and confirmed. Then a method of studying the correspondence of dimensions depending on the exposure time using test models was proposed and mathematical modeling in the form of regression univariate analysis. In the following, it is proposed to determine the influence of the layer height on the exposure time. Further, it is proposed to determine the significance of individual technological factors among themselves and their influence on the defects obtained because of printing. Building a regression analysis model, determining the correlation of technological parameters and their influence on quality indicators. Determination of the coefficient of determination of the constructed model.

Synergistic effect of microorganisms and a direct current electric field on X70 steel corrosion in a near-neutral solution

In this paper, the corrosion behavior of X70 steel in the near-neutral simulated soil solution (NS4 solution) under the synergistic effect of sulfate reducing bacteria (SRB) and a direct current electric field (DCEF) were explored. The corrosion rate was determined with the electrochemical technique and the corrosion morphology and corrosion products were respectively characterized by SEM and XPS. In the sterile solution, corrosion morphology of X70 steel was pitting and the corrosion rate increased with the increase in DCEF intensity and exposure time. When DCEF was absent, the corrosion rate of X70 steel in bacterial NS4 solution was faster than that in the sterile solution and the corrosion morphology was general corrosion. The acceleration effect of DCEF on corrosion was more significant than that of SRB. Under the synergistic effect of SRB and DCEF, when DCEF intensity increased below 500 V/m, the metabolic activity of SRB was gradually enhanced and the corrosion rate of X70 steel decreased. The protective effect of biofilm weakened the acceleration effect of DCEF on corrosion and the corrosion behavior was controlled by SRB corrosion. When DCEF intensity increased above 1000 V/m, SRB cells were inactivated and the corrosion rate of X70 steel increased. The corrosion behavior of X70 steel was controlled by DCEF. Based on the above research results, preventative actions were proposed.

Scaling features in high-concentrations PM2.5 evolution: the Ignored factor affecting scarlet fever incidence.

As an acute respiratory disease, scarlet fever has great harm to public health. Some evidence indicates that the time distribution pattern of heavy PM2.5 pollution occurrence may have an impact on health risks. This study aims to reveal the relation between scaling features in high-concentrations PM2.5 (HC-PM2.5) evolution and scarlet fever incidence (SFI). Based on the data of Hong Kong from 2012 to 2019, fractal box-counting dimension (D) is introduced to capture the scaling features of HC-PM2.5. It has been found that index D can quantify the time distribution of HC-PM2.5, and lower D values indicate more cluster distribution of HC-PM2.5. Moreover, scale-invariance in HC-PM2.5 at different time scales has been discovered, which indicates that HC-PM2.5 occurrence is not random but follows a typical power-law distribution. Next, the exposure-response relationship between SFI and scale-invariance in HC-PM2.5 is explored by Distributed lag non-linear model, in conjunction with meteorological factors. It has been discovered that scale-invariance in HC-PM2.5 has a nonlinear effect on SFI. Low and moderate D values of HC-PM2.5 are identified as risk factors for SFI at small time-scale. Moreover, relative risk shows a decreasing trend with the increase of exposure time. These results suggest that exposure to short-term clustered HC-PM2.5 makes individual more prone to SFI than exposure to long-term uniform HC-PM2.5. This means that individuals in slightly-polluted regions may face a greater risk of SFI, once the PM2.5 concentration keeps rising. In the future, it is expected that the relative risk of scarlet fever for a specific region can be estimated based on the quantitative analysis of scaling features in high-concentrations PM2.5 evolution.

Spectroscopic detection of chromatin uncoiling and chromosome alignment in neuronal-like cells under exposure to low intensity magnetic fields

In this manuscript we reported the results of our studies concerning the response of vibration bands in deoxyribonucleic acid region in neuronal-like cells under exposure to static and 50 Hz electromagnetic fields using Fourier Transform Infrared spectroscopy. This technique was chosen because it is able to detect alteration of vibration bands of chemical compounds even induced by small stress agents. The aim of this study was to investigate the response of chromatin and chromosome to low intensity electromagnetic fields at values similar to manmade electromagnetic fields. The phosphate bands of asymmetric and symmetric stretching mode (representative of deoxyribonucleic acid spectral region) were observed to decrease after 3 h exposure at 1 mT (both static and 50 Hz magnetic field). Prolonging time exposure or increasing the intensity of applied magnetic field induced a low increasing in intensity of these vibration bands. This finding can be explaining assuming that chromatin uncoiling occurred at low intensity of the field and that increasing time exposure or magnetic field intensity caused an increasing of the torque on chromosome inducing an alignment along the direction of the field.

Research on the spontaneous combustion of the goaf at different advancing distances based on the dynamic evolution of porosity

Spontaneous combustion of residual coal in the goaf is one of the main disasters in coal mines. Understanding the law of spontaneous combustion of residual coal can effectively prevent coal mine fires. This paper establishes a dynamic evolution model of overburden caving and porosity in the goaf using PFC numerical simulation software, and compares and analyzes the dynamic changes in porosity and the spontaneous combustion zone at advancing distances of 50 m, 70 m, and 100 m. The results show that when the working face advances 100 m, the porosity in the caving zone of the goaf decreases from 0–0.6 to 0.16–0.3. The range of the spontaneous combustion zone on the return air side expands from 42m-50 m to 39m–61 m, and on the inlet side, it expands from 0 to 22m–50 m. With increased exposure time, the spontaneous combustion zone range shifts slightly forward to 32m–55 m on the inlet side and 21m–49 m on the return side. This study reveals the dynamic evolution law of the spontaneous combustion zone in the goaf under the influence of different advancing distances and exposure times, which can assist in preventing goaf fires.

Effect of μ precipitation and γ′ evolution on intra-/intergranular strength of Ni-Co-Cr-based superalloys after 800 ℃ thermal exposure

The initiation of microscopic defects and the microstructural stability are crucial factors in determining the tensile strength and failure mechanism of Ni-Co-Cr-based superalloys. This study involved the long-term thermal exposure of Ni-Co-Cr-based superalloys at 800 ℃ and their elevated-temperature tensile testing at 750 ℃ to investigate the microstructural and properties evolution. A 100 h-exposure led to the formation of a significant number of μ precipitates rich in refractory elements at the grain boundaries, particularly on the large-sized γ′ precipitate surfaces. The intragranular γ′ precipitates considerably coarsened with an increasing thermal exposure duration while its volume fraction remained relatively constant. Cracks tended to nucleate preferentially at the μ phase interface during high-temperature tensile testing, leading to the breakage of the γ/γ′ precipitates and formation of pores owing to crack propagation. The dislocation motion as a deformation response of the intragranular γ/γ′ precipitates to tensile testing was dominated by a shearing mechanism, with a portion of the intragranular γ′ precipitates deforming through dislocation shearing. The primary failure mechanism during high-temperature tensile testing changed from intergranular to intragranular with an increasing exposure time. Investigating the relationship between the phase evolution and failure mechanism will enhance our understanding of the fracture behavior of Ni-Co-Cr-based superalloy hot-end structural parts.

Relative resistance of Salmonella serotypes (Typhimurium, Infantis, and Reading) to peroxyacetic acid on chicken wings

Peroxyacetic acid (PAA) is widely used as an antimicrobial in poultry processing. Recent salmonellosis outbreaks caused by Salmonella Infantis (SI) from chicken products and Salmonella Reading (SR) from turkey products have raised concerns about their enhanced resistance (compared to Salmonella Typhimurium [ST]) to commonly used antimicrobial interventions such as PAA. The objective of this research was to evaluate the efficacy of PAA against Salmonella serotypes (Typhimurium, Infantis and Reading), effect on product color and decomposition of PAA at different pH levels. Fresh chicken wings (0.45 kg) were inoculated with a cocktail (ca. 6 log CFU/mL) of nalidixic acid resistant ST, rifampicin resistant SI and kanamycin resistant SR. Inoculated chicken wings were immersed in PAA solutions (100 or 500 ppm; adjusted to either pH 8.5 or unadjusted natural pH) for either 10 s or 60 min to replicate treatments for chicken parts or whole carcasses, respectively. Treated chicken wings were rinsed in buffered peptone water (100 mL) containing sodium thiosulfate (0.1 %), serially diluted in peptone water supplemented with 200 ppm of nalidixic acid, rifampicin or kanamycin for enumeration of ST, SI, and SR respectively, and plated on APC Petrifilm. Immersion of chicken wings in 500 ppm PAA for 60 min resulted in greater microbial reductions (P ≤ 0.05) of ST, SI, SR of ca. Two log CFU/mL each, compared to 10 s treatment. Regardless of concentration and pH of PAA, increased exposure time (60 min vs. 10 s) resulted in greater reductions (P ≤ 0.05) of ST, SI, SR. ST was slightly more resistant to PAA solutions than S. Infantis and S. Reading (P ≤ 0.05) for all experimental conditions (PAA conc, pH, and exposure times). Faster decomposition of PAA (100 and 500 ppm) was observed at pH 8.5 compared to unadjusted, natural pH (P ≤ 0.05). Product color (lightness, L*) was not affected regardless of the PAA concentration, exposure time or the pH.

Bond durability between geopolymer-based CFRP composite and OPC concrete substrate in seawater environments

Geopolymer binders are regarded as promising environmentally-friendly approaches for repairing damaged structures because of their excellent bonding and durability. The interfacial bonding properties between the geopolymer and the damaged structures are critical to the effectiveness of the repair, however, the durability of this interfacial bonding in complex environments remains poorly understood, impeding the application of the aforementioned repair methods. Therefore, this study investigates the durability of the interfacial bond between geopolymer and ordinary Portland cement (OPC) concrete in seawater environments, providing valuable insights for engineering applications of geopolymer-based repair techniques. The adoption of OPC concrete as the substrate was based on its widespread use as a cementitious material in existing structures. Additionally, geopolymer repair mortars and epoxy resin were utilized as the bonding matrix adhered to the OPC concrete substrates, while small-diameter carbon fiber-reinforced polymer (CFRP) bars served as reinforcement for the bonding matrix. Single-shear tests were conducted to investigate the bond strength and failure modes between the geopolymer mortar/epoxy resin and OPC concrete substrates after 90, 180, and 360 days of exposure to a seawater environment. The interfacial degradation mechanisms were captured using scanning electron microscopy (SEM) techniques. The results showed that the interface between the geopolymer repair mortar and the OPC concrete was identified as the most vulnerable component, which dominated the failure of the geopolymer-bonded OPC concrete. SEM analysis revealed an increase in the microcrack width at this interface, resulting in a 2.86-times increase in slip between the geopolymer repair mortar and the OPC concrete after 360 days. Due to the degradation of epoxy caused by seawater exposure, the failure modes of the epoxy-bonded OPC concrete transformed from OPC concrete cracking to epoxy rapture with increasing exposure time. The bond strength of post-exposure epoxy-bonded OPC concrete was higher than that of the geopolymer–bonded OPC concrete, but the former exhibited a more brittle failure behavior.

Effect of Transient Spark Discharge and Plasma Activated Water Treatments against Fusarium graminearum Infected Wheat Grains under Laboratory Conditions

Over the last decade, more and more attention has been paid to applications of non-thermal plasma in agriculture, where it is used to decontaminate various microorganisms and to improve the seed germination. In this study, we present the results of a newly developed point-to-ring NTP transient spark discharge apparatus (NTP), plasma activated water (PAW) and their combined treatment on Durum wheat and Common wheat grains under laboratory conditions. Transient spark discharge treatment was used as direct treatment while indirect treatment of wheat grains was performed by PAW produced in point-to-plane NTP transient spark apparatus. We found that the degree of grain surface decontamination was in order NTP > PAW > combined treatment. In the case of Durum wheat grain germination, all treatments increased germination with increasing exposure times, while in the case of Common wheat, PAW treatment and combined treatment did not significantly increase the grain germination. In conclusion, plasma treatment has enormous potential for use in agriculture and its possibilities need to be fully explored.

Preparation and performance study of photo-initiated self-healing self-warning microencapsulated coated fabrics

Microcracks on the surface and inside inevitably occur during processing and use. The use of photo-initiated, self-healing, self-warning microcapsules to repair and monitor these microcracks is of practical importance to prolong the life of coated fabrics. In this work, the microcapsules (EP/FA/SiO2) with SiO2 as wall material, epoxy resin, fluorescent agent and cationic photoinitiator as core material were prepared using the interfacial in situ polymerization method. The self-healing self-warning PVC coated fabric was obtained by scraper coating method. The self-healing, self-warning and mechanical properties of the coated fabric were characterized. The results show that the microcapsules have an encapsulation efficiency of 79 % and a core-wall structure. The wall thickness is about 200 nm and the particle size is 1.7 μm. The microcapsules have excellent thermal stability below 320 °C. The microcapsules have good dispersion in the PVC coating surface and the repair agent has good wettability in the PVC coating surface. When the cuts expand, the previously embedded microcapsules break open and release the fluorescent active ingredient and the repair agent of the capsule core. Under UV light irradiation, the scratches may show a yellow fluorescence to indicate the location of the damage to the coating. The repair agent (epoxy resin) fills the cuts and then polymerizes with the cationic photoinitiator under UV light. As the exposure time increases, the cut gradually narrows and the strength of the coated fabric increases. After 36 h of UV exposure, the cut disappears and the strength of the coated fabric is 742 N, reaching the strength (768 N) of the fabric before scratching. This indicates that the coated fabric has a good photo-initiated self-healing effect.

A growth phase analysis on the influence of light intensity on microalgal stress and potential biofuel production

It is urgent to find alternatives to fossil fuels to mitigate the effects of climate change. High light intensity during microalgal growth can promote lipid and carbohydrate accumulation (feedstocks to biofuels). However, more research needs to be done concerning the effect of this factor on microalgal productivity and biochemical composition from a growth phase point of view. This study evaluated the impact of high light intensities (291, 527 and 1107 μmol m−2 s−1) on Chlorella vulgaris growth in synthetic wastewater, nutrient assimilation and biochemical composition in late-exponential and stationary growth phases. Under the highest light intensity, a higher growth rate (0.54 ± 0.02 d−1) and maximum productivity (166 ± 13 mg/L d−1) were achieved. Also, nutrient removal efficiencies at the late-exponential phase reached 97.0 ± 0.2 % and 98.2 ± 0.1 % for nitrogen and phosphorus, respectively. Under all light intensities tested at the stationary phase, microalgae also achieved high nutrient removal efficiencies (>95 %). Extreme light intensity (1107 μmol m−2 s−1) boosted the accumulation of carbohydrates (30 ± 3 % w/w) and lipids (13.0 ± 0.4 % w/w). Under lower light intensities, the content of these compounds did not change significantly between growth phases. The chlorophyll content decreased with the increasing light intensity and increasing exposure time. Exposing C. vulgaris to high light intensity seems promising to simultaneously treat wastewater and boost lipid and carbohydrate accumulation, which can be used for biofuel production.

Effects of phosphorus and boron on the γ″ precipitate evolution and creep properties of IN718 superalloy during long-term thermal exposure at 680 ℃

A study was conducted to investigate the effect of the combined addition of P and B on the γ″ precipitate and creep properties of IN718 superalloy under long-term thermal exposure at 680 ℃. Atomic probe tomography (APT) analysis and X-ray diffraction (XRD) results indicated that P could segregate in the γ″ precipitates in a substitutional way and then improve the stability of the γ″ precipitates when subjected to prolonged thermal exposure. No segregation of B was found in the γ″ precipitates. The addition of P and B significantly improves the creep properties of the IN718 superalloy during long-term thermal exposure at 680 ℃. By increasing the exposure time, the creep life of the high P and B alloy at 650 ℃/725 MPa initially increased, peaking at 500 h, and then decreased as the exposure time increased. However, the low P and B alloy shows a consistent decrease in creep life with increasing thermal exposure time. During a relatively short thermal exposure, the microstructural analysis indicated that the substantial enhancement in creep life of the high P and B alloy primarily stems from cross twins and Lomer-Cottrell (LC) locks. As the thermal exposure time increases, the more stable γ″ precipitates in the high P and B alloy, which directly improves the creep properties. The dominant deformation mechanism in the two alloys shifts from predominantly twin to a combination of twin, stacking fault (SF) and antiphase boundary-like (APB-like) shear γ″ precipitate with prolonged thermal exposure.

Magnetotransport and Shubnikov-de Haas oscillations in LaBi samples with different degrees of air exposure

A series of magnetotransport experiments has been designed to investigate single-crystalline LaBi samples subjected to different degrees of air exposure. As the air exposure time increases, the temperature-dependent resistance changes from the typical behaviour of a good metal to that of a bad metal, exhibiting a negative temperature coefficient. Additionally, the magnetoresistance in the sample with the longest air exposure becomes linear in the magnetic field, instead of the ubiquitous quadratic magnetoresistance observed in many other related rare-earth monopnictides. Despite these drastic changes, the Shubnikov–de Haas oscillations remain almost unaffected by air exposure — the frequency spectra and the effective masses do not vary as the air exposure time increases. Our results suggest the existence of two separate contributions to the transport data: one from the surface and the other from the bulk. Given the topological nature of LaBi, our results suggest controlled air exposure provides an effective means to distinguish between surface and bulk states.

Cytotoxic Effect of Amyloid-β1-42 Oligomers on Endoplasmic Reticulum and Golgi Apparatus Arrangement in SH-SY5Y Neuroblastoma Cells.

Amyloid-β oligomers are a cytotoxic structure that is key for the establishment of the beginning stages of Alzheimer's disease (AD). These structures promote subcellular alterations that cause synaptic dysfunction, loss of cell communication, and even cell death, generating cognitive deficits. The aim of this study was to investigate the cytotoxic effects of amyloid-β1-42 oligomers (AβOs) on the membranous organelles involved in protein processing: the endoplasmic reticulum (ER) and Golgi apparatus (GA). The results obtained with 10 μM AβOs in SH-SY5Y neuroblastoma cells showed that oligomeric structures are more toxic than monomers because they cause cell viability to decrease as exposure time increases. Survivor cells were analyzed to further understand the toxic effects of AβOs on intracellular organelles. Survivor cells showed morphological alterations associated with abnormal cytoskeleton modification 72-96 h after exposure to AβOs. Moreover, the ER and GA presented rearrangement throughout the cytoplasmic space, which could be attributed to a lack of constitutive protein processing or to previous abnormal cytoskeleton modification. Interestingly, the disorganization of both ER and GA organelles exposed to AβOs is likely an early pathological alteration that could be related to aberrant protein processing and accumulation in AD.