We analyze coronal holes present on the Sun during the extended minimum between Cycles 23 and 24, study their evolution, examine the consequences for the solar wind speed near the Earth, and compare ...it with the previous minimum in 1996. We identify coronal holes and determine their size and location using a combination of EUV observations from SOHO/EIT and STEREO/EUVI and magnetograms. We find that the long period of low solar activity from 2006 to 2009 was characterized by weak polar magnetic fields and polar coronal holes smaller than observed during the previous minimum. We also find that large, low-latitude coronal holes were present on the Sun until 2008 and remained important sources of recurrent high-speed solar wind streams. By the end of 2008, these low-latitude coronal holes started to close down, and finally disappeared in 2009, while smaller, mid-latitude coronal holes formed in the remnants of Cycle 24 active regions shifting the sources of the solar wind at the Earth to higher latitudes.
Sympathetic eruptions on the Sun have been observed for several decades, but the mechanisms by which one eruption can trigger another remain poorly understood. We present a three-dimensional MHD ...simulation that suggests two possible magnetic trigger mechanisms for sympathetic eruptions. We consider a configuration that contains two coronal flux ropes located within a pseudo-streamer and one rope located next to it. A sequence of eruptions is initiated by triggering the eruption of the flux rope next to the streamer. The expansion of the rope leads to two consecutive reconnection events, each of which triggers the eruption of a flux rope by removing a sufficient amount of overlying flux. The simulation qualitatively reproduces important aspects of the global sympathetic event on 2010 August 1 and provides a scenario for the so-called twin filament eruptions. The suggested mechanisms are also applicable for sympathetic eruptions occurring in other magnetic configurations.
Magnetic influences increase in importance in the solar atmosphere from the photosphere out into the corona, yet our ability to routinely measure magnetic fields in the outer solar atmosphere is ...lacking. We describe the scientific objectives and capabilities of the COronal Solar Magnetism Observatory (COSMO), a proposed synoptic facility designed to measure magnetic fields and plasma properties in the large‐scale solar atmosphere. COSMO comprises a suite of three instruments chosen to enable the study of the solar atmosphere as a coupled system: (1) a coronagraph with a 1.5 m aperture to measure the magnetic field, temperature, density, and dynamics of the corona; (2) an instrument for diagnostics of chromospheric and prominence magnetic fields and plasma properties; and (3) a white light K‐coronagraph to measure the density structure and dynamics of the corona and coronal mass ejections. COSMO will provide a unique combination of magnetic field, density, temperature, and velocity observations in the corona and chromosphere that have the potential to transform our understanding of fundamental physical processes in the solar atmosphere and their role in the origins of solar variability and space weather.
Key Points
Society is becoming increasingly vulnerable to the effects of space weather
The physical processes responsible for solar activity remain poorly understood
COSMO will provide key measurements to advance our understanding of solar processes and activity
We have previously isolated, expanded, and characterized a multipotent precursor cell from mammalian dermis (termed skin-derived precursors SKPs) that can differentiate into both neural and ...mesodermal progeny. In this study, we report the isolation, expansion, and characterization of a similar precursor cell from neonatal human foreskin tissue. Like their rodent counterparts, human SKPs grew in suspension as spheres in the presence of the mitogens fibroblast growth factor 2 and epidermal growth factor and expressed nestin, fibronectin, vimentin, and characteristic embryonic transcription factors. Human SKPs could be maintained in culture for long periods of time and would still differentiate into neurons, glia, and smooth muscle cells, including cells with the phenotype of peripheral neurons and Schwann cells. Clonal analysis indicated that single SKP cells were multipotent and could give rise to all of these progeny. Moreover, human SKPs apparently derive from an endogenous precursor within human foreskin; a subpopulation of dissociated primary foreskin cells could differentiate into neurons, a cell type never seen in skin, and the initial spheres to develop from skin expressed the same markers and had the same potential as do passaged SKPs. Together, these data indicate that SKPs are an endogenous multipotent precursor cell present in human skin that can be isolated and expanded and differentiate into both neural and mesodermal cell types.
Although neural stem cells hold considerable promise for treatment of the injured or degenerating nervous system, their current human sources are embryonic stem cells and fetally derived neural ...tissue. Here, we asked whether rodent and human skin-derived precursors (SKPs), neural crest-related precursors found in neonatal dermis, represent a source of functional, myelinating Schwann cells. Specifically, cultured SKPs responded to neural crest cues such as neuregulins to generate Schwann cells, and these Schwann cells proliferated and induced myelin proteins when in contact with sensory neuron axons in culture. Similar results were obtained in vivo; 6 weeks after transplantation of naive SKPs or SKP-derived Schwann cells into the injured peripheral nerve of wild-type or shiverer mutant mice (which are genetically deficient in myelin basic protein), the majority of SKP-derived cells had associated with and myelinated axons. Naive rodent or human SKPs also generated Schwann cells that myelinated CNS axons when transplanted into the dysmyelinated brain of neonatal shiverer mice. Thus, neonatal SKPs generate functional neural progeny in response to appropriate neural crest cues and, in so doing, provide a highly accessible source of myelinating cells for treatment of nervous system injury, congenital leukodystrophies, and dysmyelinating disorders.
We describe here the isolation of stem cells from juvenile and adult rodent skin. These cells derive from the dermis, and clones of individual cells can proliferate and differentiate in culture to ...produce neurons, glia, smooth muscle cells and adipocytes. Similar precursors that produce neuron-specific proteins upon differentiation can be isolated from adult human scalp. Because these cells (termed SKPs for skin-derived precursors) generate both neural and mesodermal progeny, we propose that they represent a novel multipotent adult stem cell and suggest that skin may provide an accessible, autologous source of stem cells for transplantation.
In recent times, the methods used to evaluate gastric ulcer healing worldwide have been based on visual examinations and estimating ulcer dimensions in experimental animals. In this study, the ...protective effect of rhodanine and 2,4-thiazolidinediones scaffolds compared to esomeprazole was investigated in an ethanol model of stomach ulcers in rats. Pretreatment with experimental treatments or esomeprazole prevented the development of ethanol-induced gastric ulcers. The severity of the lesions and injuries was significantly lower than that of vehicle (10% Tween 80) treated rats. Significant and excellent results were obtained with the compound 6 group, with inhibition percentage and ulcer area values of 97.8% and 12.8 ± 1.1 mm
, respectively. Synthesized compounds 2, 7 and 8 exhibited inhibition percentages and ulcer areas of 94.3% and 31.2 ± 1.1 mm
, 91. 3% and 48.1 ± 0. 8 mm
, 89. 5% and 57. 6 ± 1. 2 mm
, and 89. 1% and 60.3 ± 0. 8 mm
, respectively. These biological outcomes are consistent with the docking studies in which Compounds 7 and 8 showed remarkable binding site affinities toward human H+/K+-ATPase α protein (ID: P20648), rat H+/K+-ATPase α protein (ID: P09626), and Na+/K+-ATPase crystal structure (PDB ID:2ZXE) with binding site energies of - 10.7, - 9.0, and - 10.4 (kcal/mol) and - 8.7, - 8.5, and - 8.0 (kcal/mol), respectively. These results indicate that these test samples were as effective as esomeprazole. Likewise, immunohistochemical staining of antiapoptotic (BCL2) and tumor suppressor (P53) proteins showed strong positive marks in the10% Tween 80- treated group, opposing the mild staining results for the esomeprazole-treated group. Similarly, the staining intensity of the group treated with Compounds 2-8 was variable for both proteins.
An analysis of the sunspot observations made by Hevelius during 1642-1645 is presented. These records are the only systematic sunspot observations just before the Maunder Minimum (MM). We have ...studied different phenomena meticulously recorded by Hevelius after translating the original Latin texts. We reevaluate the observations of sunspot groups by Hevelius during this period and obtain an average value 7% greater than that calculated from his observations given in the current group database. Furthermore, the average of the active day fraction obtained in this work from Hevelius's records previous to the MM is significantly greater than the solar activity level obtained from Hevelius's sunspot observations made during the MM (70% versus 30%). We also present the butterfly diagram obtained from the sunspot positions recorded by Hevelius for the period 1642-1645. It can be seen that no hemispheric asymmetry exists during this interval, in contrast with the MM. Hevelius noted a ∼3-month period that appeared to lack sunspots in early 1645 that gave the first hint of the impending MM. Recent studies claim that the MM was not a grand minimum period, speculating that astronomers of that time, due to the Aristotelian ideas, did not record all sunspots that they observed, producing thus an underestimation of the solar activity level. However, we show that the good quality of the sunspot records made by Hevelius indicates that his reports of sunspots were true to the observations.
Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good ...measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near‐equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high‐speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign. In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth's outer radiation belt was elevated to levels more than three times higher in WHI than in WSM. Such behavior could not have been predicted using sunspot numbers alone, indicating the importance of considering variation within and between solar minima in analyzing and predicting space weather responses at the Earth during solar quiet intervals, as well as in interpreting the Sun's past behavior as preserved in geological and historical records.
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