Large-Amplitude Velocity Fluctuations in Coronal Loops: Flare Drivers?

Recent space observations of coronal lines broadening during a flare occurrence suggest that unresolved nonthermal velocity rises well above the background level before the start of the flare, defined as the start of hard X-ray emission. Using a new shell model to describe the Alfvenic turbulence inside a coronal loop, it is shown that the occurrence of high values (of the order of 100 km s-1) of the large-scale fluctuating velocity can represent an efficient trigger to a nonlinear intermittent turbulent cascade and then to the generation of a burst of dissipated energy. The numerical results of the model furnish a well-supported physical explanation for the reason why large velocity fluctuations represent the flare trigger rather than the result of the later energy deposition

Finite-time singularities and flow regularization in a hydromagnetic shell model at extreme magnetic Prandtl numbers

Conventional surveys on the existence of singularities in fluid systems for vanishing dissipation have hitherto tried to infer some insight by searching for spatial features developing in asymptotic regimes. This approach has not yet produced a conclusive answer. One of the difficulties preventing us from getting a definitive answer is the limitations of direct numerical simulations which do not yet have a high enough resolution so far as to properly describe spatial fine structures in asymptotic regimes. In this paper, instead of searching for spatial details, we suggest seeking a principle, that would be able to discriminate between singular or not-singular behavior, among the integral and purely dynamical properties of a fluid system. We investigate the singularities developed by a hydromagnetic shell model during the magnetohydrodynamic turbulent cascade. Our results show that when the viscosity is equal to the magnetic diffusivity (unit magnetic Prandtl number) singularities appear in a finite time. A complex behavior is observed at extreme magnetic Prandtl numbers. In particular, the singularities persist in the limit of vanishing viscosity, while a complete regularization is observed in the limit of vanishing diffusivity. This dynamics is related to differences between the magnetic and the kinetic energy cascades towards small scales. Finally a comparison between the three-dimensional and the two-dimensional cases leads to conjecture that the existence of singularities may be related to the conservation of different ideal invariants

The Management of Dental Practices in the Post-COVID 19 Era: An Economic and Operational Perspective

Background: In order to protect dental teams and their patients during the COVID-19 pandemic, dentists have had to adopt several measures (operating and post-operating procedures) which may increase the total treatment time and costs relating to individual protective measures. This paper will propose a thorough analysis of operating dentistry procedures, comparing the economic performance of the activity in a dental surgery before and after the adoption of these protective measures, which are required to contain the risk of SARS-COV-2 infections. Methods: The economic analysis is articulated in three approaches. Firstly, it assesses a reduction in markup by maintaining current charges (A); alternatively, it suggests revised charges to adopt in order to maintain unvaried levels of markup (B). And the third Approach (C) examines available dental treatments, highlighting how to profitably combine treatment volumes to reduce markup loss or a restricted increase in dental charges. Results: Maintaining dental charges could cause a loss in markup, even rising to 200% (A); attempting to maintain unvaried levels of markup will result in an increase in dental charges, even at 100% (B); and varying the volumes of the single dental treatments on offer (increasing those which current research indicates as the most profitable) could mitigate the economic impact of the measures to prevent the transmission of SARS-COV-2 (C). Conclusions: The authors of this paper provide managerial insights which can assist the dentist-entrepreneur to become aware of the boundaries of the economic consequences of governmental measures in containing the virus infection

A SHELL MODEL TURBULENT DYNAMO

Turbulent dynamo phenomena, observed almost everywhere in astrophysical objects and also in the laboratory in the recent VKS2 experiment, are investigated using a shell model technique to describe magnetohydrodynamic turbulence. Detailed numerical simulations at very high Rossby numbers (α2 dynamo) show that as the magnetic Reynolds number increases, the dynamo action starts working and different regimes are observed. The model, which displays different large-scale coherent behaviors corresponding to different regimes, is able to reproduce the magnetic field reversals observed both in a geomagnetic dynamo and in the VKS2 experiment. While rough quantitative estimates of typical times associated with the reversal phenomenon are consistent with paleomagnetic data, the analysis of the transition from oscillating intermittent through reversal and finally to stationary behavior shows that the nature of the reversals we observe is typical of α2 dynamos and completely different from VKS2 reversals. Finally, the model shows that coherent behaviors can also be naturally generated inside the many-mode dynamical chaotic model, which reproduces the complexity of fluid turbulence, as described by the shell technique

Evolution of fractality in space plasmas of interest to geomagnetic activity

We studied the temporal evolution of fractality for geomagnetic activity, by calculating fractal dimensions from the Dst data and from a magnetohydrodynamic shell model for turbulent magnetized plasma, which may be a useful model to study geomagnetic activity under solar wind forcing. We show that the shell model is able to reproduce the relationship between the fractal dimension and the occurrence of dissipative events, but only in a certain region of viscosity and resistivity values. We also present preliminary results of the application of these ideas to the study of the magnetic field time series in the solar wind during magnetic clouds, which suggest that it is possible, by means of the fractal dimension, to characterize the complexity of the magnetic cloud structure.Peer reviewe

Glutathione S transferase polymorphisms influence on iron overload in β-thalassemia patients

In patients with β-thalassemia iron overload that leads to damage to vital organs is observed. Glutathione S transferase (GST) enzymes have an antioxidant role in detoxification processes of toxic substances. This role is determined genetically. In this study, we correlated GSTT1 and GSTM1 genotypes with iron overload measured with direct and indirect non-invasive methods; in particular, we used serum ferritin and signal intensity of the magnetic resonance image (MRI) in 42 patients with β-thalassemia, which were regularly subjected to chelation and transfusion therapy. Multiplex polymerase chain reaction was used to determine the genotype. The loss of both alleles leads to a decreased value of liver and heart MRI-signal intensity with a consequent iron accumulation in these organs; the loss of only one allele doesn't lead to relevant overload. Serum ferritin doesn't appear to be correlated to iron overload instead. 对于β-地中海贫血患者,由于铁过量而造成重要器官受损的情况也在观察之中。谷胱甘肽S转移酶(GST) 酶类在对有毒物质进行解毒的过程中有着抗氧化剂的作用。该作用是由基因决定的。 在这份研究中,我们运用了直接和间接非侵入性的方法对基因型铁过量GSTT1 和GSTM1进行了相关性测量;特别地,我们对42位定期接受螯合和输血治疗的β-地中海贫血患者进行了血清铁蛋白和磁共振强度图像(MRI) 的测试。 多重聚合酶链反应的测试也被运用来确定该基因型。 该两种等位基因的缺失,导致了肝功能减损及心脏磁共振强度的下降,并造成了在这些器官中铁含量的积累;其中一种等位基因的缺失并不会导致过度的铁含量。血清蛋白和铁过量之间,看起来并不存在相关性

Synchronization of Small-scale Magnetic Features, Blinkers, and Coronal Bright Points

We investigate the relationship between different transients such as blinkers detected in images taken at 304 angstrom, extreme ultraviolet coronal bright points (ECBPs) at 193 angstrom, X-ray coronal bright points (XCBPs) at 94 angstrom on the Atmospheric Imaging Assembly, and magnetic features observed by the Helioseismic and Magnetic Imager during 10 yr of solar cycle 24. An automatic identification method is applied to detect transients, and the YAFTA algorithm is used to extract the magnetic features. Using 10 yr of data, we detect in total 7,483,827 blinkers, 2,082,162 ECBPs, and 1,188,839 XCBPs, respectively, with their birth rate of about 1.1 x 10(-18) m(-2) s(-1), 3.8 x 10(-19) m(-2) s(-1), and 1.5 x 10(-19) m(-2) s(-1). We find that about 80% of blinkers are observed at the boundaries of supergranules, and 57% (34%) are associated with ECBPs (XCBPs). We further find that about 61%-80% of transients are associated with the isolated magnetic poles in the quiet Sun and that the normalized maximum intensities of the transients are correlated with the photospheric magnetic flux of poles via a power law. These results conspicuously show that these transients have a magnetic origin and their synchronized behavior provides further clues toward the understanding of the coupling among the different layers of the solar atmosphere. Our study further reveals that the appearance of these transients is strongly anticorrelated with the sunspots' cycle. This finding can be relevant for a better understanding of solar dynamo and magnetic structures at different scales during the solar cycle

Electron Heating by Kinetic Alfvén Waves in Coronal Loop Turbulence

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Microglia-derived microvesicles affect microglia phenotype in glioma

Extracellular-released vesicles (EVs), such as microvesicles (MV) and exosomes (Exo) provide a new type of inter-cellular communication, directly transferring a ready to use box of information, consisting of proteins, lipids and nucleic acids. In the nervous system, EVs participate to neuron-glial cross-talk, a bidirectional communication important to preserve brain homeostasis and, when dysfunctional, involved in several CNS diseases. We investigated whether microglia-derived EVs could be used to transfer a protective phenotype to dysfunctional microglia in the context of a brain tumor. When MV, isolated from microglia stimulated with LPS/IFNg were brain injected in glioma-bearing mice, we observed a phenotype switch of tumor associated myeloid cells (TAMs) and a reduction of tumor size. Our findings indicate that the MV cargo, which contains upregulated transcripts for several inflammation-related genes, can transfer information in the brain of glioma bearing mice modifying microglial gene expression, reducing neuronal death and glioma invasion, thus promoting the recovery of brain homeostasis

The chromosphere: gateway to the corona, or the purgatory of solar physics?

I argue that one should attempt to understand the solar chromosphere not only for its own sake, but also if one is interested in the physics of: the corona; astrophysical dynamos; space weather; partially ionized plasmas; heliospheric UV radiation; the transition region. I outline curious observations which I personally find puzzling and deserving of attention.Comment: To appear in the proceedings of the 25th NSO Workshop "Chromospheric Structure and Dynamics. From Old Wisdom to New Insights", Memorie della Societa' Astronomica Italiana, Eds. Tritschler et a