Exposure Time Research Articles

Taking time: Auditory statistical learning benefits from distributed exposure.

In an auditory statistical learning paradigm, listeners learn to partition a continuous stream of syllables by discovering the repeating syllable patterns that constitute the speech stream. Here, we ask whether auditory statistical learning benefits from spaced exposure compared with massed exposure. In a longitudinal online study on Prolific, we exposed 100 participants to the regularities in a spaced way (i.e., with exposure blocks spread out over 3 days) and another 100 in a massed way (i.e., with all exposure blocks lumped together on a single day). In the exposure phase, participants listened to streams composed of pairs while responding to a target syllable. The spaced and massed groups exhibited equal learning during exposure, as indicated by a comparable response-time advantage for predictable target syllables. However, in terms of resulting long-term knowledge, we observed a benefit from spaced exposure. Following a 2-week delay period, we tested participants' knowledge of the pairs in a forced-choice test. While both groups performed above chance, the spaced group had higher accuracy. Our findings speak to the importance of the timing of exposure to structured input and also for statistical learning outside of the laboratory (e.g., in language development), and imply that current investigations of auditory statistical learning likely underestimate human statistical learning abilities.

Photometric light curve studies: potential bias induced by exposure time

Photometric light curve studies: potential bias induced by exposure time

Subcytotoxic transepidermal delivery using low intensity cold atmospheric plasma

Cold atmospheric plasma (CAP) has been utilized in various medical devices using its oxidative nature. Recent studies have provided evidence that CAP can facilitate the delivery of large, hydrophilic molecules through the epidermis to the dermis. On the other hand, a new approach called low-intensity CAP (LICAP) has been developed, allowing the plasma level to be controlled within a subtoxic range, thereby demonstrating various biological benefits without tissue damage. However, the ability of LICAP to enhance transepidermal delivery in sub-cytotoxic conditions has not been fully investigated. This study aims to determine the sub-cytotoxic range of exposure time for LICAP and, within the range, to investigate the effects of LICAP treatment on transepidermal drug delivery (TED) and mechanisms using human keratinocytes and a mouse model. For the in vitro studies, LICAP treatment was evaluated in human keratinocyte (HaCaT) cells by assessing reactive species production, DNA damage, and cytotoxicity profiles. Within the determined safety range, mechanistic analyses were conducted to examine LICAP-enhanced delivery pathways. mRNA expression and protein levels of tight and adherens junction genes were quantified, and changes in ultramicroscopic morphology of HaCaT monolayers were investigated. Intracellular delivery of fluorescein isothiocyanate (FITC)-dextran was also assessed. For the in vivo studies, E-cadherin expression and the transepidermal delivery (TED) of human epidermal growth factor (hEGF) were analyzed in LICAP-treated mouse dorsal skin. The upper safety range of LICAP exposure time, reducing cell viability by 70% (IC70 or LD30), was estimated at 34.3 s. Within the safety range, LICAP treatment downregulated multiple tight and adherens junction genes in HaCaT cells. Consistent with the in vitro results, the epidermal E-cadherin expression was reduced, and human epidermal growth factor (hEGF) was infiltrated in the dermis of the LICAP-treated mouse skin. Intercellular clefts were detected in the HaCaT cell monolayer immediately following LICAP treatment and intracellular delivery of FITC-dextran was confirmed after LICAP exposure. This study demonstrated that LICAP treatment enhances transepidermal permeation of hEGF, apparently via both paracellular and transcellular routes. Under our study conditions, LICAP treatment seems to be a novel approach to facilitate TED with low safety concerns in vitro. Further translational studies are needed for clinical evaluation.

Thematic Review of Endocrine Disruptors and Their Role in Shaping Pubertal Timing

This review examines the inconsistent effects of endocrine-disrupting chemicals (EDCs) and pollutants on pubertal timing, emphasizing the methodological challenges contributing to variability in findings. Data from nine key studies reveal that chemicals such as BPA, phthalates, and PFAS impact pubertal onset differently based on exposure timing, dosage, and sex. For instance, BPA is linked to earlier puberty in girls but delayed onset in boys, while other EDCs show mixed effects across populations. These discrepancies often arise from challenges in study design, such as the difficulty in establishing reliable control groups, accurately measuring exposures, and accounting for confounding factors like socioeconomic status, diet, and obesity. Sex-specific differences and environmental shifts during the COVID-19 pandemic, including increased indoor exposure and stress, further complicate the picture. These factors highlight the urgent need for more robust research methodologies, including standardized exposure assessments and longitudinal studies, to clarify the mechanisms driving these effects. Despite these challenges, the findings stress the importance of public health interventions, such as stricter EDC regulations, improved pollutant monitoring, and minimizing exposures during sensitive developmental windows. Addressing methodological gaps is crucial for producing reliable, actionable insights to protect adolescent development from the adverse effects of EDCs.

The influence of pre- and intratask emotional experiences on affective working memory maintenance.

In two studies conducted in 2022, we examined the effect of images that elicit incidental emotions and the timing of exposure to these images, on the maintenance of positive and negative emotions in affective working memory (AWM). In Study 1, participants viewed a negative, positive, or neutral image while maintaining the emotional intensity of positive or negative emotions in AWM (intratrial). The results showed that experiencing a negative or positive incidental emotion (but not neutral states) improved the maintenance of negative (but not positive) emotions induced by another stimulus. In Study 2, participants were randomly assigned to experimental conditions. In the first condition, they viewed an emotion-eliciting image while maintaining an emotion elicited by a different image (replicating Study 1). In the second condition, they viewed the emotion-eliciting image before maintaining an emotion elicited by a different image. The results replicated those of Study 1 and showed that the timing of experiencing the incidental emotion (before or during the task) did not affect AWM. They also suggest that maintenance of negative emotions increases irrespective of the emotional context surrounding them. These findings offer valuable theoretical insights into the role of emotional contexts in intensifying negative emotions, potentially guiding future research on interventions designed to modulate negative emotions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Objective surgical skill assessment based on automatic recognition of dissection and exposure times in robot-assisted radical prostatectomy

PurposeAssessing surgical skills is vital for training surgeons, but creating objective, automated evaluation systems is challenging, especially in robotic surgery. Surgical procedures generally involve dissection and exposure (D/E), and their duration and proportion can be used for skill assessment. This study aimed to develop an AI model to acquire D/E parameters in robot-assisted radical prostatectomy (RARP) and verify if these parameters could distinguish between novice and expert surgeons.MethodsThis retrospective study used 209 RARP videos from 18 Japanese institutions. Dissection time was defined as the duration of forceps energy activation, and exposure time as the combined duration of manipulating the third arm and camera. To measure these times, an AI-based interface recognition model was developed to automatically extract instrument status from the da Vinci Surgical System® UI. We compared novices and experts by measuring dissection and exposure times from the model’s output.ResultsThe overall accuracies of the UI recognition model for recognizing the forceps type, energy activation status, and camera usage status were 0.991, 0.998, and 0.991, respectively. Dissection time was 45.2 vs. 35.1 s (novice vs. expert, p = 0.374), exposure time was 195.7 vs. 89.7 s (novice vs. expert, p < 0.001), and the D/E ratio was 0.174 vs. 0.315 (novice vs. expert, p = 0.003).ConclusionsWe successfully developed a model to automatically acquire dissection and exposure parameters for RARP. Exposure time may serve as an objective parameter to distinguish between novices and experts in RARP, and automated technical evaluation in RARP is feasible.Trial registration number and dateThis study was approved by the Institutional Review Board of the National Cancer Center Hospital East (No.2020 − 329) on January 28, 2021.

Radioactive contamination of southeast Abai oblast, Kazakhstan, from the Chinese nuclear weapons testing program at Lop Nor: an analytical review.

Between 1949 and 1962 the Soviet Union performed atmospheric tests of nuclear weapons at the Semipalatinsk nuclear test site (SNTS) in Kazakhstan, resulting in widespread contamination of the surrounding region with radioactive fallout. Settlements in the southeast Abai oblast of Kazakhstan, close to the border with China, are not thought to have received significant fallout from the SNTS. There is, however, evidence that the study area, including Makanchi, Urdzhar and Taskesken villages, was contaminated by atmospheric nuclear tests performed by China at the Lop Nor NTS between 1964 and 1980. We identified the most reliable data indicating contamination from the Lop Nor tests from archive documents. Prompt sampling of soil performed in the area revealed elevated levels of total beta activity in the days and weeks following the Lop Nor tests. The highest activities were recorded following the thermonuclear tests in June 1967 and June 1973. Tooth enamel dosimetry using electron paramagnetic resonance methods suggests residents of the study area have been exposed to excess doses of 50-60mGy but provides no information on the source and timing of exposure. Currently, evidence of contamination of the study area from nuclear weapons testing at Lop Nor is based on limited radiation measurement data. Therefore, work will continue on the search for archival data on radiological and meteorological monitoring carried out in the study area at the time of the Lop Nor testing campaign.

Toxicological problems of tattoo removal: characterization of femtosecond laser-induced fragments of Pigment Green 7 and Green Concentrate tattoo ink.

Femtosecond lasers represent a novel tool for tattoo removal as sources that can be operated at high power, potentially leading to different removal pathways and products. Consequently, the potential toxicity of its application also needs to be evaluated. In this framework, we present a comparative study of Ti:Sapphire femtosecond laser irradiation, as a function of laser power and exposure time, on water dispersions of Pigment Green 7 (PG7) and the green tattoo ink Green Concentrate (GC), which contains PG7 as its coloring agent. The treated samples were subsequently analyzed via UV‒Vis spectroscopy, gas chromatography‒mass spectrometry (GC‒MS), SEM imaging and associated statistical analysis. We found that, on average, the discoloration efficacy of femtosecond laser treatment was comparable to that of nanosecond lasers as were the decomposition products. In fact, two primary types of fragments are produced, both of which are potentially harmful, resulting either from the decomposition of chlorinated phthalocyanine (i.e., PG7) or from the active chlorination of naphthalene impurities. However, the outcomes for the PG7 and GC treatments differed significantly from each other from several points of view. The spectral intensity patterns of GC and PG7 were distinct, depending on the treatment conditions, and showed linearity with power only in the case of GC. Additionally, the relative ratios of the fragment products differed significantly, with the production rate showing a linear dependence on power only in the case of GC and no discernible trend for PG7. Shape and size distribution of the generated particles were highly dependent on the type of sample. Femtosecond laser irradiation of GCs primarily produces nanoparticles with a homogeneous size distribution, which are typically considered nontoxic. Large aggregates also formed, exhibiting a regular shape. In contrast, PG7 yielded rods and needles with aspect ratios similar to those of toxic fibers.

Prospects of cold plasma in enhancing food phenolics: analyzing nutritional potential and process optimization through RSM and AI techniques

Consumption of plant-based food is steadily increasing and follows an augmented trend owing to their nutritive, functional, and energy potential. Different bioactive fractions, such as phenols, flavanols, and so on, contribute highly to the nutritive profile of food and are known to have a sensitivity toward higher temperatures. This limits the applicability of traditional thermal treatments for plant products, paving the way for the advancement of innovative and non-thermal techniques such as pulsed electric field, microwave, ultrasound, cold plasma, and high-pressure processing. Among these techniques, cold plasma would be an operative choice in plant-based applications due to their higher efficacy, greenness, chemical exclusivity, and quality retention. The efficiency of the plasma process in ensuring the bioactive potential depends on several factors, such as feeding gas, input voltage, exposure time, pressure, and current flow. This review explains in detail the optimization of process parameters of the cold plasma technique, ensuring greater extractability or retention of total phenols and antioxidant potential. Response surface methodology (RSM) is one of the common techniques involved in the optimization of these course factors. It also covers the convention of artificial intelligence-based methods, such as artificial neural networks (ANN) and genetic algorithms (GA), in evaluating the data on process parameters. The review critically examines the strengths of each optimization tool in determining the optimal process parameters for maximizing phenol retention and antioxidant activity. The ascendancy of these techniques was mentioned in the studies regarding fruit, vegetables, and their products, and they can also be applied to other food products.

Selected microwave irradiation effectively inactivates airborne avian influenza A(H5N1) virus

The highly pathogenic avian influenza A(H5N1) virus threatens animal and human health globally. Innovative strategies are crucial for mitigating risks associated with airborne transmission and preventing outbreaks. In this study, we sought to investigate the efficacy of microwave inactivation against aerosolized A(H5N1) virus by identifying the optimal frequency band for a 10-min exposure and evaluating the impact of varying exposure times on virus inactivation. A(H5N1) was aerosolized and exposed to various microwave frequencies ranging from 8 to 16 GHz for a duration of 10 min. Viral titers were quantified using TCID50, and inactivation was assessed by comparing irradiated samples to controls. The 11–13 GHz band yielded the highest inactivation, with an average 89% mean reduction in A(H5N1) titer, particularly within the 11–12 GHz range, which exhibited peak efficacy. Based on the overall results, the optimal frequency band (8–12 GHz) was further tested with exposure durations of 1, 3, and 5 min. Inactivation was time-dependent, with a 5-minute exposure resulting in a 94% mean reduction, compared to 58% and 48% for 3- and 1-minute exposures, respectively. We conclude that optimized microwave emitters in high-risk environments like poultry farms and veterinary clinics could offer a novel, non-chemical approach to mitigating avian influenza spread and outbreaks.

Silver Nanoparticles-Functionalized Textile against SARS-CoV-2: Antiviral Activity of the Capping Oleylamine Molecule.

COVID-19 disease, triggered by SARS-CoV-2 virus infection, has led to more than 7.0 million deaths worldwide, with a significant fraction of recovered infected people reporting postviral symptoms. Smart surfaces functionalized with nanoparticles are a powerful tool to inactivate the virus and prevent the further spreading of the disease. Literature reports usually focus on the role of nanomaterial composition and size dispersion in evaluating their efficacy against SARS-CoV-2. Here, the anti-SARS-CoV-2 activity of oleylamine (OAm) used as a capping agent of silver nanoparticles is quantified for the first time. Spherical hydrophobic nanoparticles with 8 ± 2 nm diameter were prepared and characterized by Fourier transform infrared, dynamic light scattering, and transmission electron microscopy techniques. Biological assays showed that microgram amounts of nanoparticles, deposited on nonwoven textile obtained from surgical masks, efficiently inactivated up to 99.6(2)% of the virus with just 2 min of exposure. The virucidal activity of the corresponding amount of free OAm has been determined as well, reaching up to 67(1)% of activity for an exposure time of 10 min. Inductively coupled plasma optical emission spectrometry results pointed out a low leaching out of the nanoparticles in contact with water or culture medium. All in all, these results propose the capping molecules as an important chemical variable to be taken into account in the design of fast, efficient, and long-lasting anti-SARS-CoV-2 coatings.

Curcumin-Loaded Lipid Nanoparticles: A Promising Antimicrobial Strategy Against Enterococcus faecalis in Endodontic Infections

Background/Objectives: This study aims to evaluate the efficacy of curcumin (CUR), a natural polyphenol with potent antimicrobial and anti-inflammatory properties, when formulated as solid lipid nanoparticles (CUR-loaded SLN) against Enterococcus faecalis. Methods: Solid lipid nanoparticles (SLNs) were prepared as a carrier for CUR, which significantly improved its solubility. SLNs made with cetyl palmitate and Tween 80 were obtained via the hot ultrasonication method. The physicochemical properties of CUR-loaded SLNs were evaluated, including their size, stability, and release profile. Antimicrobial testing was conducted against both sessile and planktonic E. faecalis populations. Cytotoxicity was assessed on human gingival fibroblasts. Results: The CUR-loaded SLNs exhibited about 200 nm and a −25 mV surface potential, and the encapsulation of CUR did not affect the physicochemical properties of SLNs. CURs were released from SLNs in a controlled and sustained manner over 100 h. The nanoparticles remained stable for at least two months when stored at 4 °C or 25 °C, making them suitable for clinical use. Antioxidant activity was confirmed through DPPH and ABTS assays. Free CUR significantly reduced the planktonic E. faecalis CFU counts by approximately 65% after 24 h of exposure. However, this inhibitory effect diminished with longer exposure times (48 and 72 h). Antimicrobial activity studies of CUR-loaded SLNs showed dose- and time-dependent effects, in the 2.5–10 µg/mL range, against both sessile and planktonic E. faecalis populations, over 24 to 72 h. The CUR-loaded SLNs showed good cytocompatibility with human fibroblasts up to 2.5 μg/mL, suggesting low toxicity. Conclusions: CUR-loaded SLNs demonstrate significant antimicrobial activity against E. faecalis, along with good cytocompatibility, indicating their potential as an effective adjunct therapy in endodontic treatments.

Evaluation of safe exposure time for two-photon microscopy imaging of acrylic-painted mock-ups

Abstract Nonlinear optical microscopies are widely used in the biological and biomedical fields, as they are non-invasive techniques that permit the safe structural and morphological characterisation of cells and tissues. They are increasingly being used in the Cultural Heritage field because of their ability to overcome some limits of the well-established optical techniques. However, since nonlinear optical microscopies use pulsed laser sources with high peak power, their application in Cultural Heritage raises concerns due to artworks' unique, priceless, and delicate nature. In this paper, we present a new method for evaluating the photo-induced damage when using a near-infrared femtosecond pulsed laser to perform two-photon excited fluorescence imaging of acrylic-painted mock-ups. In particular, we explore herein several irradiation conditions, varying the exposure time and excitation power, in order to provide useful experimental indications for safely imaging acrylic paints with two-photon microscopy.

Understanding the neurobiological mechanisms of LPS‑induced memory impairment.

In recent years, growing evidence suggests that lipopolysaccharide (LPS), a bacterial endotoxin found in the outer membrane of gram‑negative bacteria, can influence cognitive functions, particularly memory formation and retrieval. However, the underlying mechanisms through which LPS exerts its effects on memory remain incompletely understood. This review used various electronic databases, including PubMed, Scopus, and Web of Science, to identify relevant studies published between 2000 and 2024. Articles were selected based on their focus on LPS‑induced memory impairments, including experimental models, molecular pathways, and neurochemical alterations. LPS administration has been consistently shown to disrupt memory processes in both animals and humans, although the magnitude and duration of memory impairments might vary depending on factors such as dose, timing, and context of LPS exposure. Several potential mechanisms have been proposed to explain LPS‑induced memory deficits, including neuroinflammation, alterations in synaptic plasticity, disruption of neurotransmitter systems, and dysfunction of the blood‑brain barrier. Moreover, LPS has been found to activate immune signaling pathways, such as toll‑like receptors, interleukins, and microglia, which can further contribute to cognitive impairments. Such insights may pave the way for the development of targeted therapeutic interventions aimed at ameliorating memory deficits associated with conditions involving LPS exposure, including bacterial infections, sepsis, and neuroinflammatory disorders.

Using X‐ray computed microtomography (μCT) to determine subsample‐specific cosmogenic noble gas production rates of E (enstatite) chondrites

AbstractCosmic ray exposure (CRE) ages provide information about the parent bodies and source regions of meteorite classes. Cosmogenic noble gases are often used to quantify exposure time scales ranging from tens of ka to hundreds of Ma. The production rate of cosmogenic noble gases is primarily controlled by a meteorite's chemical composition. Historically, an average chemical composition for an entire meteorite class or subgroup was used to calculate production rates. At the scale needed for noble gas measurements, however, some meteorites exhibit mineral abundance variabilities that translate into chemical heterogeneities, necessitating subsample‐specific production rates. We find that the metal and sulfide content can vary significantly between ~100 and 300 mg subsamples of the same enstatite (E) chondrite, leading to &gt;10% differences in cosmogenic 21Ne production rates between subsamples. We demonstrate an approach to determining subsample‐specific production rates using E chondrites. We use electron microprobe analysis and X‐ray computed microtomography to quantify the chemical composition and abundances, respectively, of metal, sulfide, and silicate minerals in six E chondrites and calculate subsample‐specific production rates of 3He and 21Ne. By applying this method to more E chondrite subsamples alongside noble gas measurements, we may begin to address broader questions, such as whether peaks in the E chondrite CRE age distribution can be attributed to distinct impact events.

Screen time exposure and executive functions in preschool children

Increased screen time (ST) among preschool children is becoming a matter of concern globally. Although gadgets such as phones, tablets and computers might be of educational use in this population, excessive ST might impair cognitive function among preschoolers. As data on this topic in preschool children are scarce, this study sought to investigate the relationship between ST and executive functions (EFs) in this population. A total of 1016 preschool children aged 5–6 years (M = 70.8 months, SD = 4.5) were tested using the Developmental Neuropsychological Assessment (NEPSY-II) and the Dimensional Change Card Sort tests for cognitive flexibility (CF), visual working memory (WM), verbal WM, inhibition and motor persistence with parental consent, while ST was reported via a questionnaire completed by their mothers. Participants spent approximately 2 h in both active and passive ST per day, with boys spending much more time in active ST than girls. There was a very weak negative correlation between CF and both active and passive ST, and a weak negative correlation between verbal WM and both active and passive ST. Additionally, there was a very weak negative correlation between inhibition and passive ST on weekday. To ensure proper development of EFs in preschool children, ST should be limited to ≤ 1 h per day of high-quality educational/interactive content as previously determined by eminent pediatric institutions worldwide. Proven remedies that enhance EFs in children, such as physical activity and cognitive training, should be practiced regularly.

Alkali Pretreatment of Lignocellulose Feedstock Improves Morphological Structure and Biomethane Yield

This study investigates the effects of NaOH pretreatment on the microstructural distribution and biomethane released from Xyris capensis. Xyris capensis was pretreated with NaOH using 1, 2, 3, 4, and 5% w/w concentrations for 60, 45, 30, 20, and 15 min of exposure time, respectively, at a 90 °C autoclave temperature. The impacts of the pretreatment technique on microstructural arrangement, crystallinity, and functional groups were examined with a scanning electron microscope (SEM), X-ray diffraction, and Fourier transform infrared (FTIR), respectively. NaOH-pretreated and untreated feedstocks were digested at the laboratory scale at a mesophilic temperature (37 ± 2 °C) for 35 days for their biomethane potential. It was discovered from the SEM analysis that NaOH pretreatment affects the microstructural arrangement of Xyris capensis, and the sample with the longer exposure time is the most affected. The results of XRD and FTIR also indicated that NaOH pretreatment lowered the crystallinity of the feedstock and significantly influenced the functional groups at varying degrees. Biomethane yield was recorded to be 258.68, 287.80, 304.02, 328.20, 310.20, and 135.06 mL CH4/gVSadded, representing 91.53, 113.09, 125.10, 143.00, and 129.68% more increases than the untreated feedstock. It was discovered that the optimum biomethane generation was achieved when 4% w/w of NaOH concentration was utilized for 20 min. This study shows that a higher NaOH concentration with a shorter retention time is more suitable for Xyris capensis. This pretreatment method can improve the biomethane yield of Xyris capensis and can be investigated for industrial applications and its use on other lignocellulose feedstocks, especially energy grasses.

Comparison of transparency indicators of domestic samples of dental multilayer ceramics based on zirconium dioxide with indicators of a foreign analogue under different sintering modes

Relevance. New dental materials made of zirconium dioxide include 3Y-TSP and 5Y-TSP, suitable for various clinical cases, including multilayer systems that create a transparency gradient. After milling, the pre-sintered Y-TZP frames must be subjected to final sintering in 8–10 hours, although modern technologies can reduce it to 17 minutes. However, high-speed sintering can degrade the color and transparency of finished prostheses. The new monolithic ceramic systems have increased the Y3+ content to about 4 and 5 ml. %, but the indicators of layered transparency of multilayer samples after high-speed sintering remain insufficiently studied. The purpose of the work. The study of layered transparency after traditional and high-speed sintering of domestic multilayer ceramics made of zirconium dioxide and its imported analog using a laboratoryspectrophotometer. Materials and methods. Groups of 12 samples were studied: the main one (domestic production of «Ziceram ML ET») and the control one (Chinese production of «Aidite 3D Pro»), divided into subgroups «a» (traditional sintering) and «b» (high-speed sintering). The size of all samples is 15×15×1 mm, colors A1–A3, milled by removing plates from a single layer. Subgroups «a» were fired according to traditional modes with an exposure time of 30–120 minutes. Subgroup «b» was baked in a high-speed furnace in 25 minutes. Transparency was assessed using an X-Rite Ci4200 spectrophotometer using the CIE Lab* system, calculating the ratio of the «L» luminance indicators on a white and black background. Conclusions. The lightness of the layers of multilayer ceramic blanks «Ziceram ML ET» and «Aidite 3D Pro» is significantly reduced after high-speed sintering compared to traditional firing. The transparency gradients of Russian and Chinese multilayer ceramics differ, with significant changes after high-speed sintering.

Microstructural Evolution and Oxidation Resistance of Fe-30Ni-15Cr Alloy for Internal Combustion Engine Valves Under Long-Term High-Temperature Exposure and Heat Treatment

Iron–nickel-based superalloy is an ideal substitute for the expensive Inconel 625 and Inconel 751 alloys. To elucidate the evolution of the microstructure and properties of Ni30 alloy under different thermal treatment conditions, a systematic study was conducted on the microstructural transformation of the alloy’s strengthening γ′ phase following solution treatment and aging, as well prolonged exposure at 750 °C, and the oxidation behavior of the Ni30 alloy was examined. During prolonged thermal exposure, grain growth occurs mainly in the initial stage, and after 200 h, the prolonged exposure time leads to a significant coarsening of γ′ precipitates, whose area fraction increases by more than 10 times compared to their unaged state. After 100 h of aging, the alloy reaches a peak tensile strength of 1270 MPa and a yield strength of 820 MPa; after 2000 h, the alloy maintains a relatively high strength with a slight decrease in ductility. The oxidation kinetic curve of Ni30 alloy follows the quasi-parabolic oxidation law at 750 °C, and its oxidation rate is consistently lower than 0.1 g·m−2·h−1 throughout the whole oxidation process, which indicates that it has excellent oxidation resistance. The external oxide layer of Ni30 alloy shows a bilayered structure, and no obvious surface porosity or flaking of oxidation products were observed throughout the high-temperature oxidation test. This study not only contributes to the improvement of material properties, but also promotes innovation and development in the field of high-temperature engineering applications that will help to meet the increasingly stringent requirements of high-temperature working environments.

Evaluation of the frequency and risk of corona virus in different occupations of a teaching hospital in Yazd City

Introduction: Healthcare professionals are the frontline soldiers against Corona. Materials and Methods: This cross-sectional study was conducted on all personnel at a teaching hospital located in Yazd City. Each participant completed a questionnaire that included demographic information as well as their history regarding the frequency and length of daily contact with a patient infected with COVID-19. It also covered the duration of personal protective equipment (PPE) usage and alcohol-based hand rub application during direct exposure (with 1 meter) and throughout aerosolizing procedures performed on the patient. Incidence rate, Frequency rate, probability, severity rate, and risk of corona infection were evaluated among various occupational groups within the hospital. Results: 40.66% of the staff employed in the hospital were infected with corona virus. The highest frequency of corona infection was observed among nurses (51.60%). Over 90% of healthcare personnel who did not utilize PPE for 95% of their work time faced a high-risk level for the coronavirus. Physicians reported the highest number of daily exposures (averaging 27.94 exposures) and the longest exposure time (averaging 243.89 minutes). The highest risk of infection among doctors (60.93) and nurses (39.49) was observed. The nurses exhibited the highest incidence rate (51.22) and frequency rate (26.27). Conclusion: Due to a significant percentage of hospital staff with coronavirus, and with the highest infection rates occurring among nurses, adequate training for the use of PPE is necessary.