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1,619 result(s) for "X. Chu"
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NRLMSIS 2.0: A Whole‐Atmosphere Empirical Model of Temperature and Neutral Species Densities
NRLMSIS® 2.0 is an empirical atmospheric model that extends from the ground to the exobase and describes the average observed behavior of temperature, eight species densities, and mass density via a parametric analytic formulation. The model inputs are location, day of year, time of day, solar activity, and geomagnetic activity. NRLMSIS 2.0 is a major, reformulated upgrade of the previous version, NRLMSISE‐00. The model now couples thermospheric species densities to the entire column, via an effective mass profile that transitions each species from the fully mixed region below ~70 km altitude to the diffusively separated region above ~200 km. Other changes include the extension of atomic oxygen down to 50 km and the use of geopotential height as the internal vertical coordinate. We assimilated extensive new lower and middle atmosphere temperature, O, and H data, along with global average thermospheric mass density derived from satellite orbits, and we validated the model against independent samples of these data. In the mesosphere and below, residual biases and standard deviations are considerably lower than NRLMSISE‐00. The new model is warmer in the upper troposphere and cooler in the stratosphere and mesosphere. In the thermosphere, N2 and O densities are lower in NRLMSIS 2.0; otherwise, the NRLMSISE‐00 thermosphere is largely retained. Future advances in thermospheric specification will likely require new in situ mass spectrometer measurements, new techniques for species density measurement between 100 and 200 km, and the reconciliation of systematic biases among thermospheric temperature and composition data sets, including biases attributable to long‐term changes. Key Points A major, reformulated upgrade to NRLMSISE‐00 is presented using extensive new data sets from the ground to ~100 km altitude Vertical structure of the atmosphere is now self‐consistently coupled; O density now extends down to 50 km New model is warmer in upper troposphere, cooler in stratosphere and mesosphere; thermospheric N2 and O densities are lower
Tracing the stepwise oxygenation of the Proterozoic ocean
Oxygen steps in the ocean The oxygenation of the Earth's atmosphere is thought to have occurred in two steps near the beginning and the end of the Proterozoic eon, around 2,500 to 550 million years ago. The oxidation state of the ocean between these two steps and the timing of deep ocean oxygenation, however, remain poorly known. Scott et al . now use molybdenum and total organic carbon data from black shales to track the redox state of the ocean at this time. Molybdenum is an essential participant in nutrient cycling, and its availability is highly sensitive to Earth's redox state. The results provide a new narrative for the historical texture of Earth's oxygenation, and will be of relevance for the study of the events that presaged the appearance of animals on Earth. Molybdenum and total organic carbon data from black shales is used to gain insights into the redox state of the ocean. The data suggests mild oxidative weathering of the continents before ∼2,200 Myr ago, but weathering becomes more persistent and vigorous at ∼2,150 Myr ago, 200 million years after the initial rise in atmospheric oxygen. Limited availability of molybdenum after 1,800 Myr ago may have acted as a negative nutrient feedback limiting the spatial and temporal extent of sulphidic conditions. Biogeochemical signatures preserved in ancient sedimentary rocks provide clues to the nature and timing of the oxygenation of the Earth’s atmosphere. Geochemical data 1 , 2 , 3 , 4 , 5 , 6 suggest that oxygenation proceeded in two broad steps near the beginning and end of the Proterozoic eon (2,500 to 542 million years ago). The oxidation state of the Proterozoic ocean between these two steps and the timing of deep-ocean oxygenation have important implications for the evolutionary course of life on Earth but remain poorly known. Here we present a new perspective on ocean oxygenation based on the authigenic accumulation of the redox-sensitive transition element molybdenum in sulphidic black shales. Accumulation of authigenic molybdenum from sea water is already seen in shales by 2,650 Myr ago; however, the small magnitudes of these enrichments reflect weak or transient 7 sources of dissolved molybdenum before about 2,200 Myr ago, consistent with minimal oxidative weathering of the continents. Enrichments indicative of persistent and vigorous oxidative weathering appear in shales deposited at roughly 2,150 Myr ago, more than 200 million years after the initial rise in atmospheric oxygen 1 , 2 . Subsequent expansion of sulphidic conditions after about 1,800 Myr ago (refs 8 , 9 ) maintained a mid-Proterozoic molybdenum reservoir below 20 per cent of the modern inventory, which in turn may have acted as a nutrient feedback limiting the spatiotemporal distribution of euxinic (sulphidic) bottom waters and perhaps the evolutionary and ecological expansion of eukaryotic organisms 10 . By 551 Myr ago, molybdenum contents reflect a greatly expanded oceanic reservoir due to oxygenation of the deep ocean and corresponding decrease in sulphidic conditions in the sediments and water column.
Structural time series modelling for weekly forecasting of enterovirus outpatient, inpatient, and emergency department visits
Objectives : Enteroviruses pose a substantial public health challenge in Taiwan, often leading to increased healthcare visits. This study utilizes Taiwan CDC databases to analyse weekly enterovirus case data from emergency departments (EDs), as well as outpatient and inpatient settings. The objectives are to understand infection patterns through model fitting, forecast future visits for proactive epidemic management, and improve forecast accuracy by incorporating holiday effects. This approach enhances the reliability of predictions, supporting timely and effective surveillance and early detection of significant case surges. Methods : This study divides the time series data into an in-sample period (2016—2023) and an out-of-sample period covering weeks 1 to 27 in 2024. Using an expanding window approach, the analysis applies Bayesian structural time series (BSTS) models, exponential smoothing, and random forest to forecast one-week-ahead cases over the 27 weeks in 2024. The study evaluates forecast accuracy using five key metrics and identifies significant surges in cases by detecting values that exceed the 95% prediction intervals, enhancing anomaly detection. Results : The results demonstrate that BSTS models, which incorporate trends, seasonal variations, summer, and Lunar New Year holiday effects, achieve superior forecasting accuracy. Specifically, by accounting for the Lunar New Year holiday within the out-of-sample period, the models attain mean absolute percentage error (MAPE) values of 6.509% for non-ED visits and 12.645% for ED visits. Conclusions : The BSTS model effectively addresses nonlinearity and non-stationarity and adapts well to structural changes. This study highlights the importance of holiday adjustments, particularly for the Lunar New Year, in improving forecast accuracy during periods of unusual healthcare demand. These adjustments enhance the BSTS model performance for predicting irregular healthcare service demand.
Role of CCR2 in Inflammatory Conditions of the Central Nervous System
CC chemokine receptor 2 (CCR2) plays important roles in extravasation and transmigration of monocytes under inflammatory conditions. CCR2 and its ligands have been extensively studied in a range of inflammatory diseases in the central nervous system (CNS), including multiple sclerosis, Alzheimer's disease and ischemic stroke. This brief review summarizes our current understanding of the physiologic and pathologic roles of CCR2, focusing on its involvement in CNS inflammatory diseases. There appears to be a rationale for exploring therapies involving CCR2 inhibition in multiple sclerosis and ischemic stroke, but there is also evidence for immunomodulatory and protective effects of CCR2 activity during CNS inflammation. The critical balance between protective and detrimental roles of CCR2-dependent recruitment of leukocytes must therefore be carefully examined to guide safe and effective development of any therapies involving CCR2 modulation.
Migration of ferrous ions (Fe2+) during the synthesis of (Li,Fe)OHFeSe by ion exchange technology
Iron-based superconductors (FeSCs), particularly the air-stable (Li,Fe)OHFeSe, have drawn considerable attention due to their complex crystalline structures and intriguing superconducting properties. This study focuses on the synthesis of (Li,Fe)OHFeSe, using hydrothermal ion exchange technology with a nearly vacancy-free (PY) x FeSe precursor. We successfully synthesized samples in both iron-poor and iron-rich reaction systems, with the iron-rich samples exhibiting superconductivity at a transition temperature ( T c ) of 40 K, while iron-poor samples did not. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) results showed an obvious difference in Se content between the original solutions of iron-poor and iron-rich systems after the hydrothermal reaction. We propose that in iron-rich system, Fe 2+ ions migration into the (Li,Fe)OH layer from the reaction solution directly maintains the stability of the FeSe layer in the precursor, facilitating superconductivity. Conversely, in iron-poor system, Fe 2+ ions migrate into the (Li,Fe)OH layer partly from the reaction solution and partly from the FeSe layer, creating Fe vacancies in the FeSe layer, which inhibit the occurrence of superconductivity. Our findings provide valuable insights into the synthesis of intercalated FeSe-based superconducting materials and the realization of superconductivity in FeSe based superconducting materials.
Laws of environmental protection in Vietnam - Situation and solutions
Research the current situation of Vietnam's environment. Researching the real situation of the law on environmental protection: the achievements of the law on environmental protection; Current issues raised in the regulation of environmental protection legislation. Proposing and proposing major solutions to perfect the environmental protection legislation in the coming time: perfecting the environmental protection legislation; complete the national standards and technical regulations on environment; complete the regulations on environmental impact assessment; complete the regulations on waste management, especially those in urban and industrial areas; complete the regulations on environmental protection of soil, water and air; issue documents specifying the process of publication and democratization of environmental protection activities.
Computed Tomography-Guided Radiofrequency Ablation for Glossopharyngeal Neuralgia: Comparison of Cervical Computed Tomography Angiography, Transverse Process of Atlas, and Styloid Process Localization to Styloid Process Localization Alone
BACKGROUND: Glossopharyngeal neuralgia (GPN) is a condition that causes simultaneous headache and facial pain. The treatment for GPN is similar to the treatment for trigeminal neuralgia. Craniotomy microvascular decompression (MVD) or radiofrequency (RF) therapy is needed if conservative treatment with oral drugs fails. Therefore, the choice of radiofrequency therapy target is essential when treating GPN. However, finding the glossopharyngeal nerve simply by styloid process positioning is challenging. STUDY DESIGN: Prospective, clinical research study. SETTING: Department of Anesthesiology and Pain Medical Center, Jiaxing, China. OBJECTIVE: To compare the clinical effects of computed tomography (CT)-guided RF treatments on GPN when the triple localization of cervical CT, the transverse process of the atlas, and the styloid process is used to those achieved when the treatments are guided by the styloid process alone. METHODS: From August 2016 to December 2019, 19 cases of GPN neuralgia were treated by radiofrequency under the guidance of CT guided by the styloid process only. (These patients comprised the single localization (SL) of styloid process group, in whom the target of the RF treatments was the posterior medial side of half of the styloid process). From January 2020 to December 2022, 16 cases of GPN were treated by RF under the guidance of CT with cervical CTA (CT angiography), the transverse process of the atlas, and the styloid process. (These patients were placed in the TL group, in whom the target of RF therapy was the gap between the internal carotid artery and the internal jugular vein behind the horizontal styloid process at the lower edge of the transverse process of the atlas). Two percent lidocaine was injected subcutaneously at the needle insertion site, and a stylet with a 21-gauge blunt RF needle (model: 240100, manufacturer: Englander Medical Technology Co., Ltd.) was slowly advanced toward the target. After that, an RF probe was introduced, then low (2 Hz)- and high (50 Hz)-frequency currents of the RF instrument (model: PMG-230, Canada Baylis company) were applied to stimulate. A successful test was defined as a 0.5-1.0 mA current stimulation that could induce the original pain area in the pharynx, the inner ear, or both, without any abnormal irritation of the vagus or accessory nerves. If the first test was unsuccessful, then in the SL group, the needle tip’s position was adjusted to the distal end of the styloid process, and in the triple localization (TL) group, the needle tip depth’s was fine-tuned. A continuous RF treatment was given after a successful test. The RF temperature was 95ºC for 180 seconds. The time that the first puncture reached the target, the puncture paths, the success rate of the first test, the time that the glossopharyngeal nerve was found, the frequency of adjustments to the position of the RF needle, the incidence of intraoperative and postoperative complications, and the therapeutic effects were recorded. RESULTS: There were no significant differences in demographic data such as age, medical history, lateral classification, and pain score between the groups, but the TL group had a higher proportion of women than did the SL group. All patients’ puncture targets were identified according to the designed puncture path before the operation. There was no difference between the 2 groups in the time of the first puncture to the target (5.05 ± 1.22 vs. 5.82 ± 1.51, P = 0.18), and the designed puncture depth (3.65 ± 0.39 vs. 4.04 ± 0.44). The difference in puncture angles (13.48 ± 3.56 vs. 17.84 ± 3.98, P < 0.01) was statistically significant, and in 8 cases in the SL group, the glossopharyngeal nerve could not be found after 60 minutes of testing, so the RF treatment was terminated. Meanwhile, this problem occurred in only 2 cases in the TL group. There were 3 cervical hematoma cases and 2 cases of transient hoarseness and cough in the SL group, whereas the TL group had, respectively, 0 and one cases of those issues. There was no death in either group. LIMITATIONS: More clinical data should be collected in future studies. CONCLUSION: When using RF as a treatment for GPN, the glossopharyngeal nerve is easier to find by using the triple positioning of the cervical CTA, the transverse process of the atlas and the styloid process as the target to determine the anterior medial edge of the internal carotid artery behind the styloid process at the level of the lower edge of the atlas transverse process. The glossopharyngeal nerve is more difficult to locate when only the posterior medial edge of the styloid process is targeted. The single-time effective rate of 180 seconds of RF ablation at 90ºC for GPN can reach 87.5% (14/16), suggesting the treatment’s potential for clinical application. KEY WORDS: Glossopharyngeal neuralgia, radiofrequency ablation, CT-guided, styloid process, atlas transverse process, cervical CTA
Coexistence of EGFR with KRAS, or BRAF, or PIK3CA somatic mutations in lung cancer: a comprehensive mutation profiling from 5125 Chinese cohorts
Background: Determining the somatic mutations of epidermal growth factor receptor (EGFR)-pathway networks is the key to effective treatment for non-small cell lung cancer (NSCLC) with tyrosine kinase inhibitors (TKIs).The somatic mutation frequencies and their association with gender, smoking history and histology was analysed and reported in this study. Methods: Five thousand one hundred and twenty-five NSCLC patients’ pathology samples were collected, and EGFR , KRAS , BRAF and PIK3CA mutations were detected by multiplex testing. The mutation status of EGFR , KRAS , BRAF and PIK3CA and their association with gender, age, smoking history and histological type were evaluated by appropriate statistical analysis. Results: EGFR , KRAS , BRAF and PIK3CA mutation rates revealed 36.2%, 8.4%, 0.5% and 3.3%, respectively, across the 5125 pathology samples. For the first time, evidence of KRAS mutations were detected in two female, non-smoking patients, age 5 and 14, with NSCLC. Furthermore, we identified 153 double and coexisting mutations and 7 triple mutations. Interestingly, the second drug-resistant mutations, T790M or E545K, were found in 44 samples from patients who had never received TKI treatments. Conclusions: EGFR exons 19, 20 and 21, and BRAF mutations tend to happen in females and non-smokers, whereas KRAS mutations were more inclined to males and smokers. Activating and resistant mutations to EGFR-TKI drugs can coexist and ‘second drug-resistant mutations’, T790M or E545K, may be primary mutations in some patients. These results will help oncologists to decide candidates for mutation testing and EGFR-TKI treatment.
A quantitative assessment of human impacts on decrease in sediment flux from major Chinese rivers entering the western Pacific Ocean
Major rivers with high sediment or water discharge act as natural integrators of surficial processes, including human activities within their drainage basins, and they are also the primary sources of terrestrial materials entering the ocean. The river‐derived materials flux entering the coastal oceans, however, has been strongly affected by anthropogenic activities. Recent studies related to human impacts on river sediment flux have mainly focused on qualitative descriptions. Here we present a quantitative assessment of human impacts on decrease in sediment flux from nine major Chinese rivers entering the western Pacific Ocean, including Changjiang (Yangtze), Huanghe (Yellow), Zhujiang (Pearl), Songhuajiang, Liaohe, Haihe, Huaihe, Qiantangjiang, and Minjiang. During 1959–2007, dams and reservoirs, soil and water conservation programs, water consumption, as well as sand mining decreased the amount of sediment delivered to the ocean by 28, 11.5, 7.5 and 3 gigatons (Gt), respectively. If combined (50 Gt for the period 1959–2007), this reduction was close to the total decreased sediment flux (43 Gt) measured from these nine major rivers over the same period. Besides, the temporal variations in water and sediment fluxes into the ocean from these rivers generally during 1953–2007 were presented. These results are useful for further studies on Chinese and even global river‐derived material flux to the ocean and associated ecological risks.