On timescales longer than the solar cycle, long-term changes in CO2 concentration and geomagnetic field have the potential to
affect thermospheric dynamics. In this paper, we investigate the
...thermospheric dynamical response to these two factors during the Holocene,
using two sets of ∼12 000-year control runs by the coupled
thermosphere–ionosphere model, GCITEM-IGGCAS. The main results indicate that increased/decreased CO2 will enhance/weaken the thermospheric circulation throughout the Holocene, but this effect is non-linear. The cooling effect of CO2 in the thermosphere further provides plausible conditions for atmospheric tidal propagation and increases the thermospheric tidal amplitude. Geomagnetic variations induce hemispheric asymmetrical responses in the thermospheric circulation. Large changes in the circulation occur at high latitudes in the hemisphere with distant magnetic pole drift, inferring a crucial role of geomagnetic non-dipole variations in circulation changes. A positive correlation between the diurnal migrating tide (DW1) and geomagnetic dipole moment is revealed for the first time. The amplitude of DW1 in temperature will increase by ∼1–3 K for each 1×1022 A m2 increase in dipole moment.
In recent years, the research on stem cells has been more and more in-depth, and many achievements have been made in application. However, due to the small number of spermatogonial stem cells (SSCs) ...and deficiency of efficient markers, it is difficult to obtain very pure SSCs, which results in the research on them being hindered. In fact, many methods have been developed to isolate and purify SSCs, but these methods have their shortcomings. Fluorescence-activated cell sorting (FACS), as a method to enrich SSCs with the help of specific surface markers, has the characteristics of high efficiency and accuracy in enrichment of SSCs, thus it is widely accepted as an effective method for purification of SSCs. This review summarizes the recent studies on the application of FACS in SSCs, and introduces some commonly used markers of effective SSCs sorting, aiming to further optimize the FACS sorting method for SSCs, so as to promote the research of germline stem cells and provide new ideas for the research of reproductive biology.
Germline stem cells (GSCs) are germ cells with the capacities of self-renewal and differentiation into functional gametes, and are able to migrate to their niche and reconstitute the fertility of ...recipients after transplantation. Therefore, GSCs transplantation is a promising technique for fertility recovery in the clinic, protection of rare animals and livestock breeding. Though this novel technique faces tremendous challenges, numerous achievements have been made after several decades' endeavor. This review summarizes the current knowledge of GSCs transplantation and its utilization in mammals, and discusses the application prospect in reproductive medicine and animal science.
The Yangtze River Economic Belt, as crucial component of China’s “T-shaped” strategy for territorial development and economic layout, has been challenged by the unbalanced spatial distribution of ...water resources, which has seriously affected high-quality development in harmony with the social economy and ecological environmental protection. In this study, we aim to enhance the conceptual definition of water resource spatial equilibrium. Additionally, we propose a water resource spatial equilibrium evaluation model based on a variable set and partial connection number. This model effectively addresses the limitations of traditional methods by incorporating fuzzy indices and dynamic information, which have previously been overlooked. The spatiotemporal characteristics and future evolutionary trend of water resource spatial equilibrium were analyzed in 11 provinces and 110 cities in the Yangtze River Economic Belt from 1999 to 2018. The results showed that the conceptual definition of water resource spatial equilibrium involves the water resource endowment, water resource development, water resource utilization, water resource supply and demand, water resource matching, and water resource protection. The water resource spatial equilibrium in the 11 provinces gradually improved following a temporal trend; in terms of the spatial trend, the south was better than the north and the west was better than the east. These provinces were sorted as follows: Yunnan > Sichuan > Zhejiang > Jiangxi > Hunan Province > Guizhou > Hubei > Chongqing > Anhui > Jiangsu > Shanghai. The evolutionary trend increased except in Yunnan. The water resource spatial equilibrium of the 110 cities showed that the spatial trends of the three major urban agglomerations were much better than in the other regions, and the temporal trend steadily improved. The 11 provinces and 110 cities could be divided into three and five categories, respectively, according to their spatiotemporal trends. City-scale research on water resource spatial equilibrium can effectively identify and optimize the control area compared with using a provincial scale. When the control targets were set to 20%, 40%, 60%, and 80%, the proportion of the administrative area based on the city scale decreased by 1.20%, 4.99%, 10.52%, and 19.05%, respectively.
In recent decades, significant efforts have been made to characterize and understand the global pattern of ionospheric long‐term trend. However, little attention has been paid to the topside ...ionosphere trend. In this study, the unique in situ data measured by series Defense Meteorological Satellite Program (DMSP) satellites were utilized to derive the long‐term trend of the topside ionosphere for the first time. We checked carefully data quality, gap, and consistency between different satellites for both electron density and ion temperature, and compared the techniques of artificial neuron network (ANN) and multiple linear regression methods for deriving the trend. The electron density (Ne) trend in the middle and low latitudes at ~860 km around 18 MLT was derived using the ANN method from 1995–2017. The trend from DMSP observations has a mean magnitude ranging from ~ − 2% to ~2% per decade, with clear seasonal, latitude and longitude variations. The derived trend was evaluated by directly comparing with the simulated trend at 500 km from the NCAR‐TIEGCM driven by realistic changes of CO2 level and geomagnetic field. The observed and simulated trends have similar geographic distribution patterns at 18 MLT. The good agreement between the observed trend around 860 km and the simulated trend near 500 km implies that the physical processes controlling the Ne trends above the peak height might be identical. Further control simulations show that the geomagnetic field secular variation is the dominant factor of the electron density trend at around 500 km, rather than the CO2 long‐term enhancement.
Plain Language Summary
The long‐term trends in the topside ionosphere have been rarely concerned mainly due to less data availability in comparison with the lower ionosphere. The Defense Meteorological Satellite Program spacecraft with orbital height of ~860 km provide a unique opportunity to explore the distribution pattern of long‐term trends in the topside ionosphere. Based on the DMSP data after critical data quality check, we used the artificial neuron network method to derive the long‐term trend of the topside (~860 km) ionospheric electron density (Ne) around 18 MLT. We obtained, for the first time, the global, long‐term trend map of Ne. The mean magnitude of the trend ranges from ~ − 2% to ~2% per decade, which shows clear temporal and spatial variations. Moreover, in order to understand the physical mechanism of the trend, we performed a series of numerical simulations based on a first principles model of TIEGCM. The simulated results of the trend at 500 km are compared with the observed ones near 860 km, and a good agreement is found between the two, especially around the sunset time. The good agreement enables us to study the physical mechanisms of the topside ionospheric trend through control simulations. Eventually, we found that the secular variation of geomagnetic field is the dominant factor of the trends in the topside ionosphere, rather than the increased CO2.
Key Points
The long‐term trend of topside ionospheric electron density is derived from DMSP measurements for the first time
The trend at 18 MLT has a mean value ranging from ~ − 2% to ~2% per decade, with clear seasonal, latitude and longitude variations
There is good agreement between the observed and simulated trends, especially near the sunset time
This paper reports the characteristics of the topside ionospheric O+ diffusive flux (ΦO+) during both geomagnetically quiet (0 ≤ Kp ≤ 2) and moderate (2 < Kp ≤ 4) times using incoherent scatter radar ...observations at Millstone Hill (42.6°N, 288.5°E) for solar minimum from 1970 to 2018. ΦO+ partially characterizes plasma mass exchange between the upper and lower part of the topside ionosphere through diffusion and sometimes serves as upper boundary conditions for ionosphere‐thermosphere models. The altitude where the flux sign changes (mainly during daytime) is termed the transition height and the time when the flux sign changes (mainly at dawn and dusk) is termed the transition time. At quiet times, the daytime transition height is ∼100 km above the F2 peak height (hmF2) in summer, and it is about 50 km above hmF2 in other seasons; the transition time is before 18 solar local time (SLT) in spring and winter, but after 18 SLT in summer and autumn. The daytime average upward ΦO+ above the transition height shows a significant seasonal variation with a minimum of 2.2×108cm−2s−1 in summer and a maximum of 3.7×108cm−2s−1 in autumn. Under geomagnetically moderate conditions, the transition height increases by ∼20 km in spring, winter, and autumn, but moves up by about 20–50 km in summer. The transition time occurs later by ∼1 hr in summer but ∼1 hr earlier in other seasons. The mean upward ΦO+ peaks in summer and minimizes in spring.
Plain Language Summary
The topside ionospheric O+ diffusive flux (ΦO+) is a part of the total plasma flux that is a critical parameter to characterize the plasma exchange between the upper and lower part of the topside ionosphere, but has been poorly known due to lack of direct measurements. Using long‐term incoherent scatter radar (ISR) data observed at Millstone Hill for nearly five decades, this study investigates ΦO+ variations as a function of the altitude above the F2 peak height (hmF2), local time, and season in both geomagnetically quiet and moderate times, and further explores the physical mechanism causing these variations. During quiet times, the summer daytime transition height where ΦO+ changes from downward to upward along magnetic field lines occurs at ∼hmF2+100 km. However, it is usually near hmF2+50 km in other seasons. In addition, the transition time when ΦO+ changes from upward to downward at a fixed height is earlier than 18 SLT in spring and winter, but later than 18 SLT in summer and autumn. We also found that an increase in geomagnetic activity decreases the vertical gradient of plasma density during the daytime in all seasons, resulting in a ∼20 km increase in the transition height and an earlier transition time near dusk in spring, autumn, and winter, but a larger transition height change of about 20–50 km and a later transition time in summer. The change in the seasonal variations of the upward ΦO+ results from the competition between the variations of plasma diffusive velocity and density when the geomagnetic activity increases, as well as the changes in plasma vertical density profiles.
Key Points
Topside ionospheric O+ diffusive flux (ΦO+) climatology at solar minimum is derived from incoherent scatter radar data at Millstone Hill
O+ diffusive flux has seasonal, local time, and altitude dependence
Geomagnetic activity changes the spatiotemporal variations of Φ(O+) by modulating the vertical gradient of the plasma density
Ionospheric F‐region electron density is anomalously higher in the evening than during the daytime on many occasions in the summer in geomagnetic mid‐latitude regions. This unexpected ionospheric ...diurnal variation has been studied for several decades. The underlying processes have been suggested to be related to meridional winds, topside influx arising from sunset ionospheric collapse, and other factors. However, substantial controversies remain unresolved. Using a numerical model driven by the statistical topside O+ diffusive flux from the Millstone Hill incoherent scatter radar data, we provide new insight into the competing roles of topside diffusive flux, neutral winds, and electric fields in forming the evening density peak. Simulations indicate that while meridional winds, which turn equatorward before sunset, are essential to sustain the daytime ionization near dusk, the topside diffusive flux is critically important for the formation and timing of the summer evening density peak.
Plain Language Summary
The phenomenon of mid‐latitude summer nighttime anomalous ionospheric electron density enhancement (MSNA) has often been observed by both ground‐based and space‐based measurements. Previous observation and simulation studies suggested that the combined effects of neutral winds and geomagnetic field configuration are the drivers of the formation of MSNA. These results, particularly some modeling results, were obtained under some constraints and assumptions that have not been strictly validated either through critical observations or self‐consistent, first principle simulations of the coupled ionosphere‐thermosphere system. This study represents a major new advance in understanding an important controlling factor that has not been adequately addressed before. In this study, we evaluate the relative roles of topside diffusive flux, meridional winds, and electric fields over Millstone Hill, where MSNA‐like anomalies are very representative of mid‐latitudes. Using a self‐consistent coupled ionosphere‐thermosphere model, Thermosphere–Ionosphere−Electrodynamics General Circulation Model, driven by the statistical topside O+ diffusive flux from the Millstone Hill Incoherent Scatter Radar data, we found that topside O+ diffusion is critical for the formation and timing of the evening electron density peak, although it is also very clear that meridional winds, which turn equatorward before sunset, are essential for sustaining the daytime ionization near dusk. This new finding from the Millstone Hill observations may lead to an ultimate understanding of the more generic MSNA features in both the Northern and Southern Hemispheres.
Key Points
The ionospheric electron density summer evening anomaly at Millstone Hill is investigated using a joint observation and simulation analysis
Topside O+ diffusive flux is critical for anomaly formation and timing, while thermospheric winds act to preserve solar‐produced plasma
A much better understanding of the mid‐latitude summer night anomaly is achieved with observation‐informed topside specification
Background. With wrist-worn wearables becoming increasingly available, it is important to understand their reliability and validity in different conditions. The primary objective of this study was to ...examine the reliability and validity of the Lexin Mio smart bracelet in measuring heart rate (HR) and energy expenditure (EE) in people with different physical activity levels exercising at different intensities. Methods. A total of 65 participants completed one maximal oxygen uptake test and two running exercise tests wearing the Mio smart bracelet, the Polar H10 HR band, and a gas-analysis system. Results. In terms of HR measurement reliability, the Mio smart bracelet showed good reliability in a left versus right test and good test−retest reliability (p > 0.05; mean absolute percentage error (MAPE) < 10%; intraclass correlation coefficient (ICC) > 0.4). For EE measurement, the Mio smart bracelet showed good reliability in a left versus right test, good test−retest reliability on the right (p > 0.05; MAPE > 10%; ICC > 0.4), and low test−retest reliability on the left (p > 0.05; MAPE > 10%; ICC < 0.4). Regarding validity, the Mio smart bracelet showed good validity for HR measurement (p > 0.05; MAPE < 10%; ICC > 0.4) and low validity for EE measurement (p < 0.05; MAPE > 10%; ICC < 0.4). Conclusion. The Lexin Mio smart bracelet showed good reliability and validity for HR measurement among people with different physical activity levels exercising at various exercise intensities in a laboratory setting. However, the smart bracelet showed good reliability and low validity for the estimation of EE.
Sanya incoherent scatter radar (SYISR) is a newly developed phased array incoherent scatter radar in the low latitudes of China located at Sanya (18.3°N, 109.6°E), Hainan Province. The main objective ...of SYISR is to observe the ionosphere. Given its frequency and power, it should have the capability to observe the troposphere. In this study, we show several tropospheric wind experiments that may indicate radar function expansion and capability verification, although observing the troposphere will not be an operation mode in the future. Reliable radar echoes were detected by SYISR up to 20 km with a turbulence scale of 0.35 m and a frequency of 430 MHz. Generally, both the geometric (GEO) method and the velocity azimuth display (VAD) method give similar wind profiles. Above 10 km, the discrepancy between the two methods becomes nonnegligible. For the same method, the discrepancy above 15–20 km among winds derived from different zenith angle measurements is nonnegligible. The VAD methods give more reasonable results at higher altitudes. The standard deviation of the difference (SYISR radar minus the reanalysis data ERA5) for zonal wind and meridional wind was 1.1 m/s and 0.78 m/s, respectively. During rainfall, we can distinguish the spectrum of rainfall and atmospheric turbulence from the power spectrum according to the spectral widths and Doppler frequency shifts.
Purpose
Chronic inflammation contributes to the decline in muscle strength and cognitive abilities associated with aging. This study aims to clarify the effects of oral administration of
...Lacticaseibacillus paracasei
LC86 on these age-related declines, as well as its impact on the composition of gut microbiota.
Methods
Senescence-accelerated mouse prone 8 (SAMP8) mice received a 12 week regimen of LC86 (1 × 10
9
CFU/day). Muscle strength was assessed through forelimb grip strength and four-limb hanging tests. Cognitive function was evaluated through behavioral performance tests, and changes in gut microbiota were analyzed.
Results
Administration of LC86 significantly enhanced muscle strength, demonstrated by increased grip strength and higher glycogen content in the gastrocnemius muscle (
p
= 0.041,
p
= 0.017, and
p
= 0.000, respectively). Behavioral tests suggested that LC86 mitigated age-related cognitive decline. Furthermore, there was a significant decrease in serum pro-inflammatory cytokines, such as IL-6, TNF-α, and MCP-1 (
p
= 0.002,
p
= 0.000, and
p
= 0.005, respectively), and an elevation in the anti-inflammatory cytokine IL-10 level (
p
= 0.000). An increase in hepatic antioxidant capacity was observed. Significant changes in the gut microbiota composition were noted, including increased populations of
Bifidobacterium
and
Lactobacillus
and decreased levels of
Escherichia
/
Shigella
and
Bacteroides
.
Conclusion
The findings suggest that LC86 supplementation mitigates muscle weakness and cognitive impairment in aging SAMP8 mice, potentially through the modulation of inflammation and gut microbiota composition. LC86 emerges as a promising candidate for ameliorating the decline of muscular and cognitive functions associated with aging.
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