BackgroundStreptococcus mutans is known as a key causative agent of dental caries. It metabolizes dietary carbohydrate to produce acids which reduce the environmental pH leading to tooth demineralization. The ability of this bacterium to tolerate acids coupled with acid production, allows its effective colonization in the oral cavity leading to the establishment of highly cariogenic plaque. For this reason, S. mutans is the only bacterium found in significantly higher numbers than other bacteria in the dental plaque. The aim of this study was to evaluate the effect of crude extract and methanolic fraction of Z. officinale against S. mutans virulence properties.ResultsWe investigated in vitro and in vivo activity of crude extract and methanolic fraction at sub- MIC levels against cariogenic properties of S. mutans. We found that these extracts strongly inhibited a variety of virulence properties which are critical for its pathogenesis. The biofilm formation in S. mutans was found to be reduced during critical growth phases. Furthermore, the glucan synthesis and adherence was also found to be inhibited. Nevertheless, the insoluble glucan synthesis and sucrose dependent adherence were apparently more reduced as compared to soluble glucan synthesis and sucrose- independent adherence. Biofilm architecture inspected with the help of confocal and scanning electron microscopy, showed dispersion of cells in the treated group as compared to the control. The Quantitative Real Time PCR (qRT-PCR) data had shown the down regulation of the virulence genes, which is believed to be one of the major reasons responsible for the observed reduction in the virulence properties. The incredible reduction of caries development was found in treated group of rats as compared to the untreated group which further validate our in vitro data.ConclusionThe whole study concludes a prospective role of crude extract and methanolic fraction of Z. officinale in targeting complete array of cariogenic properties of S. mutans, thus reducing its pathogenesis. Hence, it may be strongly proposed as a putative anti- cariogenic agent.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0320-5) contains supplementary material, which is available to authorized users.

Aims:  To evaluate quorum sensing (QS) inhibitory activity of plant essential oils using strains of Chromobacterium violaceum (CV12472 and CVO26) and Pseudomonas aeruginosa (PAO1). Methods and Results:  Inhibition of QS‐controlled violacein production in C. violaceum was assayed using disc diffusion and agar well diffusion method. Of the 21 essential oils, four oils showed varying levels of anti‐QS activity. Syzygium aromaticum (Clove) oil showed promising anti‐QS activity on both wild and mutant strains with zones of pigment inhibition 19 and 17 mm, respectively, followed by activity in cinnamon, lavender and peppermint oils. The effect of clove oil on the extent of violacein production was estimated photometrically and found to be concentration dependent. At sub‐MICs of clove oil, 78·4% reduction in violacein production over control and up to 78% reduction in swarming motility in PAO1 over control were recorded. Gas chromatography–mass spectrometry analysis of clove oil indicated presence of many phytocompounds. Eugenol, the major constituent of clove oil could not exhibit anti‐QS activity. Conclusions:  Presence of anti‐QS activity in clove oil and other essential oils has indicated new anti‐infective activity. The identification of anti‐QS phytoconstituents is needed to assess the mechanism of action against both C. violaceum and Ps. aeruginosa. Significance and Impact of the study:  Essential oils having new antipathogenic drugs principle because of its anti‐QS activity might be important in reducing virulence and pathogenicity of drug‐resistant bacteria in vivo.

We consider recent observations of the chromospheric network, and argue that the bright network grains observed in the Ca II H & K lines are heated by an as yet unidentified quasi-steady process. We propose that the heating is caused by dissipation of short-period magnetoacoustic waves in magnetic flux tubes (periods less than 100 s). Magnetohydrodynamic (MHD) models of such waves are presented. We consider wave generation in the network due to two separate processes: (a) by transverse motions at the base of the flux tube; and (b) by the absorption of acoustic waves generated in the ambient medium. We find that the former mechanism leads to an efficient heating of the chromosphere by slow magnetoacoustic waves propagating along magnetic field lines. This heating is produced by shock waves with a horizontal size of a few hundred kilometers. In contrast, acoustic waves excited in the ambient medium are converted into transverse fast modes that travel rapidly through the flux tube and do not form shocks, unless the acoustic sources are located within 100 km from the tube axis. We conclude that the magnetic network may be heated by magnetoacoustic waves that are generated in or near the flux tubes.

The present study indicated that visual cues and diffuse noise were exceedingly common in real-world speech listening situations, while environments with negative SNRs were relatively rare. The characteristics of speech level, noise level, and SNR, together with the PLS information reported by the present study, can be useful for researchers aiming to design ecologically valid assessment procedures to estimate real-world speech communicative functions for older adults with hearing loss.

The aim of this work is to identify the physical processes that occur in the network and contribute to its dynamics and heating. We model the network as consisting of individual flux tubes, each with a nonpotential field structure, that are located in intergranular lanes. With a typical horizontal size of about 150 km at the base of the photosphere, they expand upward and merge with their neighbors at a height of about 600 km. Above a height of approximately 1000 km the magnetic field starts to become uniform. Waves are excited in this medium by means of motions at the lower boundary. We focus on transverse driving, which generates both fast and slow waves within a flux tube and acoustic waves at the interface of the tube and the ambient medium. The acoustic waves at the interface are due to compression of the gas on one side of the flux tube and expansion on the other. These longitudinal waves are guided upward along field lines at the two sides of the flux tube, and their amplitude increases with height due to the density stratification. Being acoustic in nature, they produce a compression and significant shock heating of the plasma in the chromospheric part of the flux tube. For impulsive excitation with a time constant of 120 s, we find that a dominant feature of our simulations is the creation of vortical motions that propagate upward. We have identified an efficient mechanism for the generation of acoustic waves at the tube edge, which is a consequence of the sharp interface of the flux concentration. We examine some broad implications of our results. Subject headingg s: MHD -Sun: chromosphere -Sun: magnetic fields -Sun: oscillations Online material: color figure

Objectives: The purpose of the current study was to investigate the laboratory efficacy and realworld effectiveness of advanced directional microphones (DM) and digital noise reduction (NR) algorithms (i.e., premium DM/NR features) relative to basic-level DM/NR features of contemporary hearing aids (HAs). The study also examined the effect of premium HAs relative to basic HAs and the effect of DM/NR features relative to no features. Design: Fifty-four older adults with mild-to-moderate hearing loss completed a single-blinded crossover trial. Two HA models, one a less-expensive, basic-level device (basic HA) and the other a more-expensive, advanced-level device (premium HA), were used. The DM/NR features of the basic HAs (i.e., basic features) were adaptive DMs and gain-reduction NR with fewer channels. In contrast, the DM/NR features of the premium HAs (i.e., premium features) included adaptive DMs and gain-reduction NR with more channels, bilateral beamformers, speech-seeking DMs, pinnasimulation directivity, reverberation reduction, impulse noise reduction, wind noise reduction, and spatial noise reduction. The trial consisted of four conditions, which were factorial combinations of HA model (premium vs. basic) and DM/NR feature status (on vs. off). In order to blind participants regarding the HA technology, no technology details were disclosed and minimal training on how to use the features was provided. In each condition participants wore bilateral HAs for five weeks. Outcomes regarding speech understanding, listening effort, sound quality, localization, and HA satisfaction were measured using laboratory tests, retrospective self-reports (i.e., standardized questionnaires), and in-situ self-reports (i.e., self-reports completed in the real world in real time). A smartphone-based ecological momentary assessment system was used to collect in-situ self-reports.

We examine the propagation of kink and longitudinal waves in the solar magnetic network. Previously, we investigated the excitation of network oscillations in vertical magnetic flux tubes through buffeting by granules and found that footpoint motions of the tubes can generate sufficient wave energy for chromospheric heating. We assumed that the kink and longitudinal waves are decoupled and linear. We overcome these limitations by treating the nonlinear MHD equations for coupled kink and longitudinal waves in a thin flux tube. For the parameters we have chosen, the thin tube approximation is valid up to the layers of formation of the emission features in the H and K lines of Ca ii, at a height of about 1 Mm. By solving the nonlinear, timedependent MHD equations we are able to study the onset of wave coupling, which occurs when the Mach number of the kink waves is of the order of 0.3. We also investigate the transfer of energy from the kink to the longitudinal waves, which is important for the dissipation of the wave energy in shocks. We find that kink waves excited by footpoint motions of a flux tube generate longitudinal modes by mode coupling. For subsonic velocities, the amplitude of a longitudinal wave increases as the square of the amplitude of the transverse wave, and for amplitudes near Mach number unity, the coupling saturates and becomes linear when the energy is nearly evenly divided between the two modes.

No abstract