High resolution observations of SiO masers: comparing the spatial distribution at 43 and 86 GHz

We present sub-milliarcsecond observations of SiO masers in the late-type stars IRC +10011 and Chi Cyg. We have used the NRAO Very Long Baseline Array (VLBA) to map the 43 GHz (v=1, 2 J=1-0) and the 86 GHz (v=1, 2 J=2-1) SiO masers. All the transitions have been imaged except the v=2 J=2-1 in IRC +10011. We report the first VLBI map of the v=1 J=2-1 28SiO maser in IRC +10011 as well as the first VLBA images of SiO masers in an S-type Mira variable, Chi Cyg. In this paper we have focused on the study of the relative spatial distribution of the different observed lines. We have found that in some cases the observational results are not reproduced by the current theoretical pumping models, either radiative or collisional. In particular, for IRC +10011, the v=1 J=1-0 and J=2-1 28SiO lines have different spatial distributions and emitting region sizes, the J=2-1 emission being located in an outer region of the envelope. For Chi Cyg, the distributions also differ, but the sizes of the masing regions are comparable. We suggest that the line overlaps between ro-vibrational transitions of two abundant molecular species, H2O and 28SiO, is a possible explanation for the discrepancies found between the observations and the theoretical predictions. We have introduced this overlapping process in the calculations of the excitation of the SiO molecule. We conclude that the line overlaps can strongly affect the excitation of SiO and may reproduce the unexpected observational results for the two sources studied.Comment: 16 pages, 12 figure

Spiropyran-based reversible, light-modulated sensing with reduced photofatigue

Switchable materials have tremendous potential for application in sensor development that could be applied to many fields. We are focusing on emerging area of wireless sensor networks due to the potential impact of this concept in society. Spiropyran-based sensors are probably the most studied type of photoswitchable sensing devices. They suffer from many issues but photofatigue, insufficient selectivity and lack of sensitivity are probably the most important characteristics that hinder their wider application. Here, we are address these issues and demonstrate that covalent attachment of modified spiropyran into a polymeric film significantly reduces photodegradation. The observed signal loss after 12th cycle of switching between the spiropyran and merocyanine forms is only about 27% compared to the loss of 57% of the initial signal in an equivalent experiment based on non-immobilized spiropyran. This has enabled us to demonstrate at least five reversible cycles of detection of an ion of interest (in our case H+) with minimal signal loss. Furthermore, we demonstrate that the sensitivity can be increased by incorporation of additional binding groups in the parent spiropyran molecule. Using molecular modelling to calculate the relevant bond lengths as a measure of interaction between MC and H+, the calculated increase of H-bond strength is approximately an order of magnitude for a derivative containing a methoxy group incorporated in the o-position of the parent spiropyran in comparison to the equivalent unsubstituted phenol. This theoretical result was found to correspond very well with experimental observation. As a result, we have increased the sensitivity to H+ by approximately one order of magnitude

Visualizing biological data in museums : Visitor learning with an interactive tree of life exhibit

In this study, we investigate museum visitor learning and engagement at an interactive visualization of an evolutionary tree of life consisting of over 70,000 species. The study was conducted at two natural history museums where visitors collaboratively explored the tree of life using direct touch gestures on a multi-touch tabletop display. In the study, 247 youth, aged 8-15 years, were randomly assigned in pairs to one of four conditions. In two of the conditions, pairs of youth interacted with different versions of the tree of life tabletop exhibit for a fixed duration of 10minutes. In a third condition, pairs watched a 10minute video on a similar topic. Individual responses on a 53-item exit interview were then compared to responses from a fourth, baseline condition. Contrasting with the baseline condition, visitors who interacted with the tabletop exhibits were significantly more likely to reason correctly about core evolutionary concepts, particularly common descent and shared ancestry. They were also more likely to correctly interpret phylogenetic tree diagrams. To investigate the factors influencing these learning outcomes, we used linear mixed models to analyze measures of dyads' verbal engagement and physical interaction with the exhibit. These models indicated that, while our verbal and physical measures were related, they accounted for significant portions of the variance on their own, independent of youth age, prior knowledge, and parental background. Our results provide evidence that multi-touch interactive exhibits that enable visitors to explore large scientific datasets can provide engaging and effective learning opportunities

Numerical simulations of stellar SiO maser variability. Investigation of the effect of shocks

A stellar hydrodynamic pulsation model has been combined with a SiO maser model in an attempt to calculate the temporal variability of SiO maser emission in the circumstellar envelope (CE) of a model AGB star. This study investigates whether the variations in local physical conditions brought about by shocks are the predominant contributing factor to SiO maser variability because, in this work, the radiative part of the pump is constant. We find that some aspects of the variability are not consistent with a pump provided by shock-enhanced collisions alone. In these simulations, gas parcels of relatively enhanced SiO abundance are distributed in a model CE by a Monte Carlo method, at a single epoch of the stellar cycle. From this epoch on, Lagrangian motions of individual parcels are calculated according to the velocity fields encountered in the model CE during the stellar pulsation cycle. The potentially masing gas parcels therefore experience different densities and temperatures, and have varying line-of-sight velocity gradients throughout the stellar cycle, which may or may not be suitable to produce maser emission. At each epoch (separated by 16.6 days), emission lines from the parcels are combined to produce synthetic spectra and VLBI-type images. We report here the results for v=1, J=1-0 (43-GHz) and J=2-1 (86-GHz) masers.Comment: 16 pages, 8 figures, accepted by A&

Diversity in Party Leadership in State Legislatures

Members of historically underrepresented groups—women, African Americans, Latinos, and workers—are serving in American legislatures in increasing numbers. However, legislators wield substantially greater power in the lawmaking process when they hold leadership positions. Incorporation of these groups into leadership positions could indicate fuller political representation, but scholars to date have not assessed how well these groups are represented in leadership. We analyze original data describing the backgrounds of approximately 2,200 leaders in 30 states between 2003 and 2014. The data show that, on average across states, members of these groups are as well represented in state legislative leadership positions as they are in rank-and-file membership, but there is substantial variation across states and across parties. We then ask what factors might explain this variation and explore institutional characteristics, like the number of leadership positions or leader selection methods. The results show that legislative chambers with a higher number of leadership posts tend to have more women in leadership, and that selection through elections is associated with decreased African American presence in leadership. The findings have implications for minority incorporation and influence in American politics

Multibeam Maser Survey of methanol and excited OH in the Magellanic clouds: new detections and maser abundance estimates

‘The definitive version is available at www.blackwell-synergy.com.’ Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.12888.xPeer reviewe

Blood pressure reduction and recovery of stunned myocardium in the hypertrophied hypertensive heart

Digitalitzat per Artypla

The modulation of SiO maser polarization by Jovian planets

Searching for planets in the atmosphere of AGB stars is difficult, due to confusion with the stellar wind and pulsations. The aim here is to provide a complementary strategy for planet search in such a dense environment. The polarization properties of SiO masers, especially their circular polarization, are, under certain conditions, good tracers for rapid magnetospheric events. A Jovian planet with a magnetosphere whose dipole axis is misaligned with its rotation axis, naturally provides such conditions. Here I present several models showing that the polarization will be periodically modulated. Single-dish monitoring with a sufficiently dense time sampling and a carefully calibrated polarimeter, in combination with VLBI observations, are suited to detect and locate a periodic modulation of the circular maser polarization due to a precessing Jovian magnetosphere. The phenomenon will be rare, because a favourable arrangement of maser and magnetosphere is needed, otherwise the polarization may be below the detection threshold, especially if the maser is unsaturated. Linear polarization, though exhibiting a qualitatively similar modulation, is likely to suffer more from confusion due to beam dilution, even in VLBI observations