1,363 research outputs found

    Evidence For Mixed Helicity in Erupting Filaments

    Full text link
    Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non--active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope (EIT) on the {\it Solar and Heliospheric Observatory} ({\it SOHO}), in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is in general determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament ``barbs'' is opposite in sign to and dominates that of the overlying arcade.Comment: ApJ, accepte

    Smarter irrigation scheduling in the sugarcane farming system using the Internet of Things

    Get PDF
    Better irrigation practices can lead to improved yields through less water stress and reduced water usage to deliver economic benefits for farmers. More and more sugarcane growers are transitioning to automated irrigation in the Burdekin and other regions. Automated irrigation systems can save farmers a significant amount of time by remotely turning on and off pumps and valves. However, the system could be improved if it could be integrated with tools that factor in the weather, crop growing conditions, water deficit, and crop stress, to improve irrigation use efficiency. IrrigWeb is a decision-support tool that is turned to as a solution to this problem. IrrigWeb uses CANEGRO to help farmers decide when to irrigate and how much to apply. Farmers can then use this information to plan their irrigation management. However, managing irrigation is a considerable time investment for Burdekin farmers. A tool is needed to integrate the auto-irrigation system (e.g., WiSA) and IrrigWeb to provide a smarter irrigation solution. An uplink program (WiSA to IrrigWeb) has been successfully developed and implemented as part of a pilot study. It saves farmers a significant amount of time by uploading irrigation and rainfall data automatically instead of the farmer having to input them manually. This paper focuses on developing a smarter irrigation-scheduling tool that connects IrrigWeb to WiSA. A downlink program was developed to download, calculate and apply irrigation schedules automatically. In this process, sugarcane irrigators will spend less time manually setting up irrigation schedules as it will happen automatically. The simulation results demonstrated that the downlink program could improve the scheduling by incorporating practical limitations, such as pumping capacity or pumping time constraints, that are found on the farm

    Reduced Macrophage Apoptosis is Associated with Accelerated Atherosclerosis in Low-Denstiy Lipoprotein Receptor-Null Mice

    Get PDF
    Objective— The majority of apoptotic cells in atherosclerotic lesions are macrophages. However, the pathogenic role of macrophage apoptosis in the development of atherosclerosis remains unclear. Elevated expression of Bax, one of the pivotal proapoptotic proteins of the Bcl-2 family, has been found in human atherosclerotic plaques. Activation of Bax also occurs in free cholesterol-loaded and oxysterol-treated mouse macrophages. In this study, we examined the effect of Bax deficiency in bone marrow-derived leukocytes on the development of atherosclerosis in low-density lipoprotein receptor-null (LDLR−/−) mice. Methods and Results— Fourteen 8-week-old male LDLR−/− mice were lethally irradiated and reconstituted with either wild-type (WT) C57BL6 or Bax-null (Bax−/−) bone marrow. Three weeks later, the mice were challenged with a Western diet for 10 weeks. No differences were found in the plasma cholesterol level between the WT and Bax−/− group. However, quantitation of cross sections from proximal aorta revealed a 49.2% increase (P=0.0259) in the mean lesion area of the Bax−/− group compared with the WT group. A 53% decrease in apoptotic macrophages in the Bax−/− group was found by TUNEL staining (P\u3c0.05). Conclusions— The reduction of apoptotic activity in macrophages stimulates atherosclerosis in LDLR−/− mice, which is consistent with the hypothesis that macrophage apoptosis suppresses the development of atherosclerosis

    Publisher Correction: Towards an ecosystem model of infectious disease

    Get PDF
    Correction to: Nature Ecology & Evolution https://doi.org/10.1038/s41559-021-01454-8, published online 17 May 2021

    Towards an ecosystem model of infectious disease

    Get PDF
    Increasingly intimate associations between human society and the natural environment are driving the emergence of novel pathogens, with devastating consequences for humans and animals alike. Prior to emergence, these pathogens exist within complex ecological systems that are characterized by trophic interactions between parasites, their hosts and the environment. Predicting how disturbance to these ecological systems places people and animals at risk from emerging pathogens-and the best ways to manage this-remains a significant challenge. Predictive systems ecology models are powerful tools for the reconstruction of ecosystem function but have yet to be considered for modelling infectious disease. Part of this stems from a mistaken tendency to forget about the role that pathogens play in structuring the abundance and interactions of the free-living species favoured by systems ecologists. Here, we explore how developing and applying these more complete systems ecology models at a landscape scale would greatly enhance our understanding of the reciprocal interactions between parasites, pathogens and the environment, placing zoonoses in an ecological context, while identifying key variables and simplifying assumptions that underly pathogen host switching and animal-to-human spillover risk. As well as transforming our understanding of disease ecology, this would also allow us to better direct resources in preparation for future pandemics

    The X10 Flare on 2003 October 29: Triggered by Magnetic Reconnection between Counter-Helical Fluxes?

    Get PDF
    Vector magnetograms taken at Huairou Solar Observing Station (HSOS) and Mees Solar Observatory (MSO) reveal that the super active region (AR) NOAA 10486 was a complex region containing current helicity flux of opposite signs. The main positive sunspots were dominated by negative helicity fields, while positive helicity patches persisted both inside and around the main positive sunspots. Based on a comparison of two days of deduced current helicity density, pronounced changes were noticed which were associated with the occurrence of an X10 flare that peaked at 20:49 UT, 2003 October 29. The average current helicity density (negative) of the main sunspots decreased significantly by about 50. Accordingly, the helicity densities of counter-helical patches (positive) were also found to decay by the same proportion or more. In addition, two hard X-ray (HXR) `footpoints' were observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI} during the flare in the 50-100 keV energy range. The cores of these two HXR footpoints were adjacent to the positions of two patches with positive current helicity which disappeared after the flare. This strongly suggested that the X10 flare on 2003 Oct. 29 resulted from reconnection between magnetic flux tubes having opposite current helicity. Finally, the global decrease of current helicity in AR 10486 by ~50% can be understood as the helicity launched away by the halo coronal mass ejection (CME) associated with the X10 flare.Comment: Solar Physics, 2007, in pres

    Superconductivity in a Mesoscopic Double Square Loop: Effect of Imperfections

    Full text link
    We have generalized the network approach to include the effects of short-range imperfections in order to analyze recent experiments on mesoscopic superconducting double loops. The presence of weakly scattering imperfections causes gaps in the phase boundary B(T)B(T) or Φ(T)\Phi(T) for certain intervals of TT, which depend on the magnetic flux penetrating each loop. This is accompanied by a critical temperature Tc(Φ)T_c(\Phi), showing a smooth transition between symmetric and antisymmetric states. When the scattering strength of imperfections increases beyond a certain limit, gaps in the phase boundary Tc(B)T_c(B) or Tc(Φ)T_c(\Phi) appear for values of magnetic flux lying in intervals around half-integer Φ0=hc/2e\Phi_0=hc/2e. The critical temperature corresponding to these values of magnetic flux is determined mainly by imperfections in the central branch. The calculated phase boundary is in good agreement with experiment.Comment: 9 pages, 6 figure

    Water wave propagation and scattering over topographical bottoms

    Get PDF
    Here I present a general formulation of water wave propagation and scattering over topographical bottoms. A simple equation is found and is compared with existing theories. As an application, the theory is extended to the case of water waves in a column with many cylindrical steps
    • …
    corecore