Search

Peptic ulcer recurrent bleeding occurs in 20% to 30% of patients after standard endoscopic hemostasis, particularly within 4 days after the procedure. The application of additional tranexamic acid (TXA) to the ulcer may enhance hemostasis. This study investigated the effectiveness of TXA powder application on bleeding ulcers during endoscopic hemostasis. This study enrolled patients who had peptic ulcer bleeding between March 2022 and February 2023. After undergoing standard endoscopic therapy, the patients were randomly assigned to either the TXA group or the standard group. In the TXA group, an additional 1.25 g of TXA powder was sprayed endoscopically on the ulcer. Both groups then received 3 days of high-dose (8 mg/h) continuous infusion proton pump inhibitor therapy. Second-look endoscopy was conducted on days 3 to 4. The primary end point of early treatment failure was defined as ulcer recurrent bleeding within 4 days or major stigmata of recent hemorrhage on the second-look endoscopy. Sixty patients (30 in each group) with peptic ulcer bleeding and balanced baseline characteristics were randomly assigned to a treatment group. The early treatment failure rate was lower in the TXA group (6.7%) than in the standard group (30%) (P =.042). The freedom from treatment failure periods for 4 and 28 days was significantly longer in the TXA group than in the standard group (P =.023). No adverse events from TXA were recorded. The precise delivery of topical TXA alongside standard endoscopic hemostasis reduced the early treatment failure rate in patients with bleeding peptic ulcers. (Clinical trial registration number: NCT05248321.) [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding the stability of irradiation-induced voids in materials is important for engineering material's swelling behavior under irradiation. In-situ TEM offers a spatial and temporal resolution that is suitable for investigating the evolution of voids under irradiation. However, the in-situ videos have often been too large to be analyzed manually, leaving the valuable data underutilized. We developed a deep learning-based semantic segmentation model to consistently study the growth and shrinkage of voids in nickel under 1 MeV krypton ion irradiation at various temperatures from 525 °C to 650 °C. With a foil thickness near 100 nm and ion flux of 6.3 × 1011 ions⋅ cm−2⋅s−1, the pre-existing voids, which were created beforehand by irradiation at 600 °C to 0.5 dpa, shrank at low temperatures and grew at high temperatures under irradiation, where the transition occurred at 575 °C (∼0.5 T M). The observed stability transition provided new insight for the shrinkage mechanism of voids under irradiation. In addition, an annealing experiment on nickel, previously irradiated at 600 °C to 3 dpa, was performed sequentially at 650 °C to 720 °C to reveal the shrinkage rate of void as a function of temperature and void size. The advantage of combining computer vision and in-situ TEM to obtain comprehensive void evolution was demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract High entropy alloys (HEAs) have been considered for applications in nuclear reactors due to their promising mechanical properties, corrosion and radiation resistance. It has been suggested that sluggish diffusion kinetics and lattice distortion of HEAs can enhance the annihilation of irradiation-induced defects, giving rise to a higher degree of tolerance to irradiation damage. In order to understand the irradiation effects in HEAs and to demonstrate their potential advantages over conventional austenitic stainless steels (SS), we performed in-situ ion irradiation experiments with 1 MeV krypton at 300 °C on two HEAs and a 316H SS under an identical irradiation condition. The irradiation introduced a high density of dislocation loops in all materials, and the microstructural evolution as a function of dose was similar for HEAs and 316H SS. Nanoindentation tests showed that the degree of irradiation hardening was also comparable between them. The similar microstructural evolution and irradiation hardening behavior between the HEAs and 316H indicate that, at low temperatures (≤300 °C), the irradiation damage of fcc alloys is not sensitive to compositional variation and configurational entropy. [ABSTRACT FROM AUTHOR]

Irradiation induced microstructural changes in the NF709 austenitic stainless steel were investigated under 1 MeV Kr ion irradiations to a dose of 3 dpa at room temperature (RT), 300, 400, 500 and 600 °C, and a dose of 20 dpa at RT. The irradiation-induced defects and the stability of precipitates were characterized with transmission electron microscopy (TEM). Frank dislocation loops were observed in all the irradiated samples, and the loop sizes were much larger at 600 °C than those at lower temperatures. “Raft” defect structures, formed through self-alignment of small dislocation loops, were also observed in all irradiated samples. M 23 C 6 precipitates were amorphorized under irradiations at RT and 300 °C, but remained to be crystalline at 400 °C and above. MX precipitates were stable under irradiations at RT up to 20 dpa, and at temperatures below 600 °C to 3 dpa. At 600 °C, some MX precipitates were observed to dissolve during in-situ irradiation, suggesting possible precipitate instability at this irradiation temperature. [ABSTRACT FROM AUTHOR]

Microstructural changes resulted from neutron irradiation and post-irradiation annealing in a high-temperature ultra-fine precipitate strengthened (HT-UPS) stainless steel were characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Three HT-UPS samples were neutron-irradiated to 3 dpa at 500 °C, and after irradiation, two of them were annealed for 1 h at 600 °C and 700 °C, respectively. Frank dislocation loops were the dominant defect structure in both the as-irradiated and 600 °C post-irradiation-annealed (PIAed) samples, and the loop sizes and densities were similar in these two samples. Unfaulted dislocation loops were observed in the 700 °C PIAed sample, and the loop density was greatly reduced in comparison with that in the as-irradiated sample. Nano-sized MX precipitates were observed under TEM in the 700 °C PIAed sample, but not in the 600 °C PIAed or the as-irradiated samples. The titanium-rich clusters were identified in all three samples using APT. The post-irradiation annealing (PIA) caused the growth of the Ti-rich clusters with a stronger effect at 700 °C than at 600 °C. The irradiation caused elemental segregations at the grain boundary and the grain interior, and the grain boundary segregation behavior is consistent with observations in other irradiated austenitic steels. APT results showed that PIA reduced the magnitude of irradiation induced segregations. [ABSTRACT FROM AUTHOR]

Fe and Fe-Cr (Cr = 10–16 at.%) specimens were neutron-irradiated at 300 °C to 0.01, 0.1 and 1 dpa. The TEM observations indicated that the Cr significantly reduced the mobility of dislocation loops and suppressed vacancy clustering, leading to distinct damage microstructures between Fe and Fe-Cr. Irradiation-induced dislocation loops in Fe were heterogeneously observed in the vicinity of grown-in dislocations, whereas the loop distribution observed in Fe-Cr is much more uniform. Voids were observed in the irradiated Fe samples, but not in irradiated Fe-Cr samples. Increasing Cr content in Fe-Cr results in a higher density, and a smaller size of irradiation-induced dislocation loops. Orowan mechanism was used to correlate the observed microstructure and hardening, which showed that the hardening in Fe-Cr can be attributed to the formation of dislocation loops and α′ precipitates. [ABSTRACT FROM AUTHOR]

Background & Aims: We used a new, semi-parametric method to estimate life expectancy and expected years of life lost (EYLL) after diagnosis of gastric cancer and assess whether patients' sex or tumor type or location had any effects. Methods: We performed a nationwide retrospective cohort study of 35,576 patients with gastric cancer who were registered in the Taiwan Cancer Registry from 1998 through 2007; data were collected until the end of 2010. The Monte Carlo method and tables in Taiwan National Vital Statistics database were matched to the cohort reference populations on the basis of age and sex. The estimated regression line and the survival curve of reference populations were used to extrapolate the survival curve beyond 2010. We compared patients' age at diagnosis, life expectancy, and EYLL based on sex, tumor type, and location. Results: In Taiwan, gastric cancer is more prevalent among men, and 88.6% of tumors are adenocarcinomas. Patients with adenocarcinoma of the gastric cardia have shorter life expectancies and greater EYLL than those with noncardia tumors (P < .05). Women with gastric adenocarcinoma are diagnosed at a younger age and have longer life expectancies but more EYLL than men with such tumors (P < .05). The estimated years of life saved if gastric adenocarcinoma is diagnosed at an early stage and cured are 22,827 years (2.62 years/case) for women and 33,700 years (1.97 years/case) for men. Conclusion: Among patients with gastric cancer, men and patients with adenocarcinomas of the cardia have shorter life expectancies and more EYLL. Early detection of gastric adenocarcinoma can increase life expectancy. [Copyright &y& Elsevier]

Children with Developmental Coordination Disorder (DCD) show deficits in the covert orienting of visuospatial attention, suggesting an underlying issue in attentional disengagement and/or inhibitory control. However, an important theoretical issue that remains unclear is whether the pattern of deficits varies with DCD severity. Fifty-one children with moderate DCD (MDCD), 24 children with severe DCD (SDCD), and 38 typically developing (TD) children participated in the study. Their performance was compared on the covert orienting of visuospatial attention task (COVAT), specifically the voluntary control mode. Results showed that the pattern of performance differed between groups. At a short stimulus–response asynchrony (350ms), the difference in response times for validly and invalidly cued trials was similar for all three groups. However, at the longer SOA (800ms), both DCD groups continued to show a relative disadvantage for responses that followed invalid cues. This suggests that a deficit in response inhibition and/or attentional disengagement is manifest in children with both moderate and severe DCD. The implications of these findings for theory and treatment are discussed. [Copyright &y& Elsevier]

Background: Patients with comorbidities have an increased risk of ulcer rebleeding, especially within the 28 days after endoscopic therapy. Omeprazole infusion can prevent rebleeding after endoscopic therapy in patients with peptic ulcer bleeding. However, the optimal duration is uncertain, especially for those patients with comorbidities. Objective: To determine whether prolonged low-dose intravenous omeprazole could reduce rebleeding for patients with comorbidities. Design: A prospective randomized control study. Setting: National Cheng Kung University, Tainan, Taiwan. Patients: A total of 147 patients with comorbidities and peptic ulcer bleeding controlled by endoscopic hemostasis were enrolled. Interventions: The enrolled patients were randomized into either the 7-day low-dose group or the 3-day high-dose group, who received 3.3 mg/h or 8 mg/h continuous omeprazole infusion, respectively. After omeprazole infusion, oral esomeprazole 40 mg every day was given. Main Outcome Measurements: To compare the rebleeding rates within 28 days after gastroscopy between the 2 study groups. Results: The 7-day cumulative rebleeding rate was similar between the 2 groups (9.5% vs 9.7%, P > .05), but the 7-day low-dose group had a lower risk of rebleeding between the 8th and 28th day compared with the 3-day high-dose group (0% vs 10.7%, P = .03; relative risk, 0.52 [95% CI, 0.43-0.63]). The Kaplan-Meier curves confirmed that the 7-day low-dose group had a significantly higher cumulative rebleeding-free proportion between the 8th and 28th day than the 3-day high-dose group (P = .02, log-rank test). Conclusions: In Asian patients, prolonged low-dose omeprazole infusion for 7 days may reduce peptic ulcer rebleeding during the first 28 days in patients with comorbidities. [Copyright &y& Elsevier]

Helium bubble formation was examined by scanning/transmission electron microscopy (S/TEM) in Fe-9/10Cr binary alloys and two dispersion strengthened nanostructured alloys (CNA3 and 14YWT containing 5–10 nm diameter carbide and oxide particles, respectively) after ex-situ and in-situ He implantation to ~10,000 appm at 500 to 900 °C. The combination of high-resolution STEM images and electron energy loss spectroscopy (EELS) revealed that the Y-Ti-O nanoparticles in 14YWT were uniformly distributed and exhibited a one-to-one relationship for bubble attachment to the nanoclusters. In the in-situ experiment at 900 °C, grain boundary cracking was severe in the Fe-10Cr model alloy, but not in the nanostructured alloys. From 500 to 900 °C, the bubble size generally increased with increasing irradiation temperature, while the bubble density decreased with increasing temperature. At the same temperatures, the bubble size in the implanted materials was in the order of Fe-9/10Cr > CNA3 > 14YWT, while the bubble density showed the opposite order. The observed bubble number densities for the nanostructured alloys are comparable to the nanoparticle density, suggesting that the nanoparticles in both alloys were effective in trapping He. Our results indicate that very high He concentrations can be managed in nanostructured alloys by sequestering the helium into smaller bubbles (which leads to a lower volume swelling value) and to shield He from the grain boundaries. This can be attributed to the much higher sink strength associated with the nanoclusters or the He trapping ability between different types of nanoclusters. [Display omitted] [ABSTRACT FROM AUTHOR]

Alloy 709 stainless steel (A709 SS) has gained an increased interest in nuclear applications due to its advanced properties at high temperatures over the widely used Type 316 SS. However, how this alloy behaves under irradiation with concurrent environmental factors, such as mechanical deformation and/or thermal annealing, has not been studied. In this work, we used in-situ ion irradiation inside a transmission electron microscope (TEM) to investigate the effects of irradiation on the microstructures of A709 SS samples with different prior processing histories, including as-received, annealed, and creep-deformed. It was found that, compared to room temperature irradiation, 600°C irradiation led to larger dislocation loop sizes and lower loop densities. With 600°C irradiation, the creep-deformed sample, which had the highest precipitate density and the highest dislocation density, had the smallest loop size and the lowest loop density compared to others. This observation has been rationalized with quantitative evaluation of the sink strength factors in each sample. This study shows that in-service deformation can significantly affect the irradiation performance in structural materials at reactor operating conditions. [ABSTRACT FROM AUTHOR]

The attractive mechanical properties and superior resistance to void-swelling make ferritic/martensitic alloys a promising structural material for advanced nuclear reactors. However, one anomaly that has intrigued researchers for more than 50 years is the proportion of two types of dislocation loops in Fe and Fe-Cr alloys with Burger vectors b =½<111> and b =<100>. Although the possible mechanisms responsible for the presence of 〈100〉 loops continue to be the subject of intense modeling studies, there remains incomplete experimental understanding of fundamental irradiation processes in Fe(Cr) alloys. Here, the dose dependence of the irradiation-induced microstructural evolution was examined from 0 to 20 displacement per atom (dpa) in high purity Fe and Fe-10Cr during simultaneous dual-beam (1 MeV Kr + 10 appm He/dpa) irradiation at 435 °C. We experimentally revealed that the mechanism for the formation of 〈100〉 loops may not follow the conventional simple dislocation reaction between two ½<111> loops. Real-time dynamic formation and evolution of defects including black dot loops, loop coarsening, loop decoration, network dislocations, and cavities were demonstrated. Several results indicated that the addition of Cr and He could impede dislocation loop motion. The evolution of the defect size/density and relative fraction of ½<111> vs 〈100〉 loops were quantitatively summarized. With increasing dose, ½<111> loops became the dominant type of loop in both materials. Notably, 〈100〉 loops were predominantly observed near grain boundaries only for pure Fe, while arrays of nanoscale black dot defects composing the 〈100〉 loop strings were observed in plenty in Fe-10Cr. [Display omitted] [ABSTRACT FROM AUTHOR]

To study the helium effects and their interactions with displacement damage in irradiated materials, an in situ dual-ion beam irradiation capability with transmission electron microscopy was recently established at the IVEM-Tandem Facility at Argonne National Laboratory. Pure nickel was irradiated in situ individually with 1 MeV Kr ions for displacement damage study, 16 keV He ions for helium implantation, and simultaneously with 1 MeV Kr ions and 16 keV He ions at the rate of 1 at.% He/dpa to study the interaction of helium and displacement damage at 500 °C. Helium bubbles were formed and segregated within dislocation loops during the He implantation experiment and no bubbles were observed outside the loops. The loop size increased with increasing helium concentration. In contrast, helium bubbles were formed uniformly in the matrix when nickel was irradiated simultaneously with 1 MeV Kr ions and 16 keV He ions. It is suggested that the uniformly-distributed defect clusters formed under 1 MeV Kr ion irradiation serve as trapping sites of helium atoms resulting in homogeneous nucleation of helium bubbles under the dual-ion beam irradiation in nickel. • In situ TEM study of interaction of helium implantation and displacement damage under dual-ion beams. • Heterogenous distribution of helium bubbles was observed inside dislocation loops under 16 keV helium ion implantation. • Distinctly different distributions of helium bubbles and dislocation loops were observed by TEM in pure nickel under in situ single and dual-beam irradiations. [ABSTRACT FROM AUTHOR]

To evaluate the potential of high entropy alloys (HEAs) for nuclear applications, two HEAs, Al 0.3 CoCrFeNi and CoCrFeMnNi, and a conventional Type 316H stainless steel (SS) were irradiated with 1 MeV krypton ions at 500 °C up to 1 dpa, and examined in-situ with a transmission electron microscope (TEM). After irradiation, a high density of ordered L1 2 nanoparticles was observed in Al 0.3 CoCrFeNi. In contrast, no phase transformation was observed in CoCrFeMnNi and 316H SS. In the thin foil regions of TEM samples, stacking-fault tetrahedra were observed in the HEAs. In the thick foil regions, interstitial dislocation loops were observed for all alloys, and the areal loop density increased linearly with foil thickness. The Al 0.3 CoCrFeNi had the largest loop size (the lowest density), followed by the CoCrFeMnNi and then the 316H SS. The higher loop nucleation rate in the 316H SS was attributed to carbon content. The degree of irradiation hardening was slightly lower for the HEAs than for the 316H SS, which is a promising sign for the nuclear application of HEAs at high temperatures. Bright-field TEM micrographs of Al0.3CoCrFeNi, CoCrFeMnNi and 316H SS irradiated with 1 MeV Kr ions at 500 °C to 1 dpa. All images were taken at similar foil thickness near 110 zone axis with g = 200. The two high entropy alloys exhibited significantly larger size and smaller density of dislocation loops as compared with the 316H stainless steels. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: Airlines can use market positioning to identify the major strengths and weaknesses of their services. The empirical analysis examines the international airlines operating on the Taipei–Tokyo and Taipei–Osaka routes. The multiple correspondence analysis results illustrate the relative positions of airlines, service attributes, and travelers’ characteristics in a perceptual map. The cluster analysis clearly identifies two groups of airlines that compete on particular services. The findings suggest that each airline can simultaneously adopt strategies to maintain and enhance its current strengths and to strengthen attributes in which it is lacking. [Copyright &y& Elsevier]

The evolution of irradiation-induced defects in additively manufactured (AM) austenitic stainless steel was investigated in situ by 1 MeV Kr ion irradiation at 450 and 600 °C in a transmission electron microscope. Cellular dislocation structure in AM steel act as sink/trap sites for the irradiation-induced defects, resulting in the lower density and smaller dislocation loops in AM steel than conventional forged (CF) steel at 450 °C. The higher stacking fault energy and local stress concentration induced by cellular dislocation structure in AM steel promotes the unfaulting process and the formation of network dislocation at 600 °C. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The thermal conductivity of UO 2 fuel needs to be high enough to dissipate the heat generated from the fission reaction. Since grain size affects thermal conductivity and grain size can evolve with irradiation, it is critical to understand in-reactor UO 2 grain growth. Most studies of grain growth in UO 2 are based on thermally driven processes at elevated temperatures. However, studies have shown that grain growth can occur even at cryogenic temperatures by ballistic processes. Such irradiation-induced grain growth in UO 2 is yet to be studied. Advanced in-situ Kr ion irradiation and transmission electron microscopy were systematically performed on nanocrystalline UO 2 thin films at temperatures ranging from 50 K to 1073 K; grain growth was observed at all temperatures. A combination of manual and machine learning techniques was used to measure and plot grain size evolution against irradiation fluence at various irradiation temperatures. The machine learning method has significantly improved the analysis efficiency and reduced human labors. The grain diameter data were fitted using classical grain growth and thermal spike models to describe grain growth kinetics with and without irradiation effect. Grain growth during low temperature irradiation (≤ 475 K) can be well described by the thermal spike model. Above 475 K, there were additional thermally assisted processes that further accelerate the grain growth. At the highest irradiation temperature about 1075 K, both irradiation-induced dislocation loops and cavities/bubbles were observed to form in the UO 2. The effects of irradiation-induced defects on grain growth kinetics are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

In situ irradiations with 1 MeV Kr ions at 50~613 K up to a fluence of 6.25 × 1014 ions/cm2 (~1.25 displacements per atom, dpa) have been performed on pre-aged dilute Cu-0.9%Co, Cu-0.9%Fe and Cu-0.8%Cr alloys containing uniform matrix dispersions of coherent precipitates in order to study the effects of initial precipitate sink strength, damage dose and irradiation temperature on radiation-induced coherency loss of precipitates. Coherent precipitates with different point defect sink strengths (2πNd, where N and d are the precipitate density and diameter) were used in this work to examine potential differences in atomic relaxation during absorption of point defects. In all cases, irradiation to low doses (<~1 dpa) was very effective at inducing loss of precipitate coherency. At low sink strengths (~1013 m−2), loss of precipitate coherency could be induced for doses ~0.01 dpa. This suggests there might be an efficient preferential medium-range strain-induced bias for absorption of interstitial defects due to tensile strains emanating from the undersized precipitates, which induces relatively rapid loss of coherency at low precipitate sink strengths. High precipitate sink strength (~1014 m−2) conditions were relatively resistant to the radiation-induced loss of coherency (requiring higher doses approaching ~1 dpa) and this might be due to nearly equal numbers of interstitial and vacancy defects arriving at the precipitate interface for such high sink strength conditions. The precipitate coherency loss was observed to have a weak dependence on irradiation temperature. Molecular dynamics simulations confirm a strong effect of precipitate sink strength on the probability of interstitial absorption at precipitates. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing as a new processing technique can produce unique microstructure that is difficult to achieve using conventional techniques. In this study, we have investigated the creep behavior of 316 L stainless steel produced by a laser powder bed fusion process at temperatures of 550, 600 and 650 °C and stresses between 175 and 300 MPa. We found that additively-manufactured 316 L stainless steel had a higher stress dependence of the minimum creep rate than conventionally-made Type 316 SS, which could be attributed to the dislocation cell structure resulting from the printing process. The dislocation cell structure was unstable under creep, evolving into a uniform dislocation structure under the test conditions. While internal porosity in AM 316 L SS may serve as nucleation sites of creep voids and may be responsible for a relatively lower creep life, additively-manufactured 316 SS did not show inferior creep ductility when compared with conventionally-made 316 SS. The creep life of AM 316 L SS could be improved by stabilizing dislocation cell structure and/or reducing internal porosity through an optimized additive manufacturing process. [ABSTRACT FROM AUTHOR]

A vein structure, which becomes more pronounced with increasing ion dose, was found on the surface of polycrystalline HOPG (highly oriented pyrolytic graphite) implanted by ex situ C+ (up to 1.8 × 1017 ions/cm2), and in situ Ar+ in a transmission electron microscope (TEM). These veins are found to be independent of the crystallographic orientations and are associated with the formation of pores. Underneath the veins, a triangular-shaped core was formed with the graphite platelet inside the core displaced up towards the surface. A macro-scale 'ruck&tuck' geometry was thus generated at these triangle structure boundaries. Progressive movement of dislocations along basal planes during irradiation was observed, and a mechanistic model was proposed on this basis to explain the vein formation. A small increase of c -spacing was observed with irradiation but it is believed that macro-scale vein formation plays a more vital role in the dimensional and property changes in polycrystalline graphite, especially when a stress gradient is present. The model proposed also explains the change of thermal expansion in HOPG with irradiation. Together with Heggie's 'ruck&tuck' and Barsoum's 'ripplocations' models, the present model is considered to have provided an additional experimentally proven mechanism responsible for irradiation behaviour in graphite materials. Image 1 [ABSTRACT FROM AUTHOR]