Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review

Modeling the Subsurface Structure of Sunspots

While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There are two main hypotheses for the subsurface structure of sunspots: the monolithic model and the cluster model. Local helioseismology is the only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do not yet allow helioseismology to probe the internal structure with sufficient confidence to distinguish between the monolith and cluster models, the development of physically realistic sunspot models are a priority for helioseismologists. This is because they are not only important indicators of the variety of physical effects that may influence helioseismic inferences in active regions, but they also enable detailed assessments of the validity of helioseismic interpretations through numerical forward modeling. In this paper, we provide a critical review of the existing sunspot models and an overview of numerical methods employed to model wave propagation through model sunspots. We then carry out an helioseismic analysis of the sunspot in Active Region 9787 and address the serious inconsistencies uncovered by \citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find that this sunspot is most probably associated with a shallow, positive wave-speed perturbation (unlike the traditional two-layer model) and that travel-time measurements are consistent with a horizontal outflow in the surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic

The Origin, Early Evolution and Predictability of Solar Eruptions

Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt

Synergistic effects of ethanol medicinal plant extracts with erythromycin against skin strains of staphylococci with inducible phenotype of MLS-resistance

Introduction. One of the main ways to control microorganisms’ resistance to antibiotics is to find substances that are able to overcome it and potentiate antibiotics action, in particular to neutralize the antibiotic-inactivating enzymes or block the active efflux of antibiotic from microbial cells. Every year there is a growing interest in the therapeutic potential of herbal active compounds as modifiers of antibiotic resistance including MLS-resistance (macrolide-lincosamide-streptoramin B). It should be emphasized that a number of biologically active substances of plant origin can potentiate antimicrobial activity of erythromycin (ERY) against MLS-resistant staphylococci. The present study was designed to investigate the antibacterial and synergistic effects of eight Ukrainian ethanol medicinal plant extracts with erythromycin against skin strains of staphylococci with inducible phenotype of MLS-resistance. Material & methods. S. aureus and S. epidermidis strains were tested for susceptibility to antibiotics of MLS-group by disk diffusion test. Effective antimicrobial concentrations of plant extracts and erythromycin were determined by two-fold serial dilution in nutrient agar and broth. Combinatory effects between organic extracts and ERY were assessed using the checkerboard assay against tested strains to evaluate culture growth in the presence of two antimicrobials with different concentrations. Results & discussion. The Alnus incana L. fruits extract was the most potent inhibitor against tested strains (MIC 40.625-162.5 µg/mL); while Geranium pratense L. rhizomes extract exhibited the least antimicrobial activity (MIC 650-2,600 µg/mL). The Alnus incana L. fruits extract and the Geranium pratense L. rhizomes extract showed synergistic effect with erythromycin against 100% strains of staphylococci (average FICI 0.028 – 0.057; p<0.001). In the presence of 1/4 MIC of ERY Alnus incana L. fruits extract antimicrobial concentration was decreased in 32-64 times and Geranium pratense L. rhizomes extract antimicrobial concentration was decreased in 64-256 times. Ethanol extracts of Betula verrucosa L. buds (average FICI 0.473±0.20), Arctostaphylos uva-ursi (L.) Spreng. leaves (average FICI 0.143±0.18) and Tamarix ramosissima Ledeb. leaves (average FICI 0.189±0.29) showed synergic action with erythromycin against 71.4-85.7% tested strains. Ethanol extracts of Sanguisorba officinalis L. roots showed non-interactive action with antibiotic against 42.8% isolates of staphylococci. Additive interaction with erythromycin for this extract was observed against 28.6% and synergic action against 28.6% strains (average FICI 0.812±0.52). Biota orientalis (L.) Endl. (Platycladus orientalis (L.) Franco) fruits extract and Cotinus coggygria Scop. (Rhus cotinus R.) leaves extract exhibited non-interactive action with antibiotic against all tested strains (average FICI 2.0±0.0). Experimental data indicate that combination of plant extracts with macrolides in therapeutic regimens against MLS-resistant staphylococci is promising, particularly for the treatment of pyoderma. The introduction of combined chemotherapy in clinical practice can actually help to solve two problems of modern medicine - slow the process of microorganisms (such as staphylococcus) resistance to antibiotics acquiring and improve treatment of infections caused by resistant strains. Detection of bacteria antibiotic resistance modifiers in various plants stimulates to their intensive phytochemical study for isolation and identification of the active components. It will help to investigate the mechanisms of synergy on the molecular level. Conclusion. BAC of medicinal and aromatic plants potentiate antimicrobial activity of macrolides against skin isolates of staphylococci with inducible MLS-resistance. Alnus incana L. fruits ethanolic extract demonstrates the best direct antimicrobial activity and in combination with ERY synergistically inhibits the growth of S. aureus and S. epidermidis MLS-resistant strains. Ethanolic extracts of Geranium pratense L. rhizomes, Arctostaphylos uva-ursi (L.) Spreng. leaves, Tamarix ramosissima Ledeb. leaves and Betula verrucosa L. buds also exhibit synergistic effect with ERY against skin isolates of staphylococci with inducible MLS-resistance

Synthesis and Thermoelectric Properties of PbTe-SnTe Solid Solutions

There are presents X-ray results and measurements of thermoelectric parameters (thermoelectric electromotive force α, specific electrical conductivity σ, and coefficient of thermal conductivity k) for materials on the base of PbTe-SnTe system. The dimensionless thermoelectric figure of merit ZT ≈ 0,3 received for thermoelectric samples p-Pb&lt;sub&gt;0.4&lt;/sub&gt;Sn&lt;sub&gt;0.6&lt;/sub&gt;Te obtained by cold pressing method in complex with annealing