71 research outputs found
The new HiVIS spectropolarimeter and spectropolarimetric calibration of the AEOS telescope
We designed, built, and calibrated a new spectropolarimeter for the HiVIS
spectrograph (R 12000-49000) on the AEOS telescope. We also did a polarization
calibration of the telescope and instrument. We will introduce the design and
use of the spectropolarimeter as well as a new data reduction package we have
developed, then discuss the polarization calibration of the spectropolarimeter
and the AEOS telescope. We used observations of unpolarized standard stars at
many pointings to measure the telescope induced polarization and compare it
with a Zemax model. The telescope induces polarization of 1-6% with a strong
variation with wavelength and pointing, consistent with the altitude and
azimuth variation expected. We then used scattered sunlight as a linearly
polarized source to measure the telescopes spectropolarimetric response to
linearly polarized light. We then made an all-sky map of the telescope's
polarization response to calibrate future spectropolarimetry.Comment: PASP 118, June 200
PPAK Integral Field Spectroscopy survey of the Orion Nebula: Data Release
We present a low-resolution spectroscopic survey of the Orion nebula which
data we release for public use. In this article, we intend to show the possible
applications of this dataset analyzing some of the main properties of the
nebula. We perform an integral field spectroscopy mosaic of an area of ~5' X 6'
centered on the Trapezium region of the nebula, including the ionization front
to the south-east. The analysis of the line fluxes and line ratios of both the
individual and integrated spectra allowed us to determine the main
characteristics of the ionization throughtout the nebula.The final dataset
comprises 8182 individual spectra, which sample each one a circular area of
\~2.7" diameter. The data can be downloaded as a single row-stacked spectra
fits file plus a position table or as an interpolated datacube with a final
sampling of 1.5"/pixel. The integrated spectrum across the field-of-view was
used to obtain the main integrated properties of the nebula, including the
electron density and temperature, the dust extinction, the Halpha integrated
flux (after correcting for dust reddening), and the main diagnostic line
ratios. The individual spectra were used to obtain line intensity maps of the
different detected lines. These maps were used to study the distribution of the
ionized hydrogen, the dust extinction, the electron density and temperature,
and the helium and oxygen abundance...Comment: 13 pages, 8 figures, accepted for publishing in Astronomy &
Astrophysic
Multisite spectroscopic seismic study of the beta Cep star V2052 Oph: inhibition of mixing by its magnetic field
We used extensive ground-based multisite and archival spectroscopy to derive
observational constraints for a seismic modelling of the magnetic beta Cep star
V2052 Ophiuchi. The line-profile variability is dominated by a radial mode
(f_1=7.14846 d^{-1}) and by rotational modulation (P_rot=3.638833 d). Two
non-radial low-amplitude modes (f_2=7.75603 d^{-1} and f_3=6.82308 d^{-1}) are
also detected. The four periodicities that we found are the same as the ones
discovered from a companion multisite photometric campaign (Handler et al.
2012) and known in the literature. Using the photometric constraints on the
degrees l of the pulsation modes, we show that both f_2 and f_3 are prograde
modes with (l,m)=(4,2) or (4,3). These results allowed us to deduce ranges for
the mass (M \in [8.2,9.6] M_o) and central hydrogen abundance (X_c \in
[0.25,0.32]) of V2052 Oph, to identify the radial orders n_1=1, n_2=-3 and
n_3=-2, and to derive an equatorial rotation velocity v_eq \in [71,75] km
s^{-1}. The model parameters are in full agreement with the effective
temperature and surface gravity deduced from spectroscopy. Only models with no
or mild core overshooting (alpha_ov \in [0,0.15] local pressure scale heights)
can account for the observed properties. Such a low overshooting is opposite to
our previous modelling results for the non-magnetic beta Cep star theta Oph
having very similar parameters, except for a slower surface rotation rate. We
discuss whether this result can be explained by the presence of a magnetic
field in V2052 Oph that inhibits mixing in its interior.Comment: 12 pages, 6 figures and 5 tables; accepted for publication in MNRAS
on 2012 August 1
Evaluation of the anti-inflammatory effects of synthesised tanshinone I and isotanshinone I analogues in zebrafish
During inflammation, dysregulated neutrophil behaviour can play a major role in a range of chronic inflammatory diseases, for many of which current treatments are generally ineffective. Recently, specific naturally occurring tanshinones have shown promising anti-inflammatory effects by targeting neutrophils in vivo, yet such tanshinones, and moreover, their isomeric isotanshinone counterparts, are still a largely underexplored class of compounds, both in terms of synthesis and biological effects. To explore the anti-inflammatory effects of isotanshinones, and the tanshinones more generally, a series of substituted tanshinone and isotanshinone analogues was synthesised, alongside other structurally similar molecules. Evaluation of these using a transgenic zebrafish model of neutrophilic inflammation revealed differential anti-inflammatory profiles in vivo, with a number of compounds exhibiting promising effects. Several compounds reduce initial neutrophil recruitment and/or promote resolution of neutrophilic inflammation, of which two also result in increased apoptosis of human neutrophils. In particular, the methoxy-substituted tanshinone 39 specifically accelerates resolution of inflammation without affecting the recruitment of neutrophils to inflammatory sites, making this a particularly attractive candidate for potential pro-resolution therapeutics, as well as a possible lead for future development of functionalised tanshinones as molecular tools and/or chemical probes. The structurally related β-lapachones promote neutrophil recruitment but do not affect resolution. We also observed notable differences in toxicity profiles between compound classes. Overall, we provide new insights into the in vivo anti-inflammatory activities of several novel tanshinones, isotanshinones, and structurally related compounds
Photometric multi-site campaign on the open cluster NGC 884 I. Detection of the variable stars
CONTEXT: Recent progress in the seismic interpretation of field beta Cep
stars has resulted in improvements of the physics in the stellar structure and
evolution models of massive stars. Further asteroseismic constraints can be
obtained from studying ensembles of stars in a young open cluster, which all
have similar age, distance and chemical composition.
AIMS: To improve our comprehension of the beta Cep stars, we studied the
young open cluster NGC 884 to discover new B-type pulsators, besides the two
known beta Cep stars, and other variable stars.
METHODS: An extensive multi-site campaign was set up to gather accurate CCD
photometry time series in four filters (U, B, V, I) of a field of NGC884.
Fifteen different instruments collected almost 77500 CCD images in 1286 hours.
The images were calibrated and reduced to transform the CCD frames into
interpretable differential light curves. Various variability indicators and
frequency analyses were applied to detect variable stars in the field. Absolute
photometry was taken to deduce some general cluster and stellar properties.
RESULTS: We achieved an accuracy for the brightest stars of 5.7 mmag in V,
6.9 mmag in B, 5.0 mmag in I and 5.3 mmag in U. The noise level in the
amplitude spectra is 50 micromag in the V band. Our campaign confirms the
previously known pulsators, and we report more than one hundred new multi- and
mono-periodic B-, A- and F-type stars. Their interpretation in terms of
classical instability domains is not straightforward, pointing to imperfections
in theoretical instability computations. In addition, we have discovered six
new eclipsing binaries and four candidates as well as other irregular variable
stars in the observed field.Comment: Accepted for publication in Astronomy and Astrophysics, 21 pages, 14
figures, 4 tables. The full appendix is available at
http://www.ster.kuleuven.be/~sophies/Appendix.pdf (74 MB, 169 pages, 343
figures, 1 table
Automated High-Content Live Animal Drug Screening Using C. elegans Expressing the Aggregation Prone Serpin α1-antitrypsin Z
The development of preclinical models amenable to live animal bioactive compound screening is an attractive approach to discovering effective pharmacological therapies for disorders caused by misfolded and aggregation-prone proteins. In general, however, live animal drug screening is labor and resource intensive, and has been hampered by the lack of robust assay designs and high throughput work-flows. Based on their small size, tissue transparency and ease of cultivation, the use of C. elegans should obviate many of the technical impediments associated with live animal drug screening. Moreover, their genetic tractability and accomplished record for providing insights into the molecular and cellular basis of human disease, should make C. elegans an ideal model system for in vivo drug discovery campaigns. The goal of this study was to determine whether C. elegans could be adapted to high-throughput and high-content drug screening strategies analogous to those developed for cell-based systems. Using transgenic animals expressing fluorescently-tagged proteins, we first developed a high-quality, high-throughput work-flow utilizing an automated fluorescence microscopy platform with integrated image acquisition and data analysis modules to qualitatively assess different biological processes including, growth, tissue development, cell viability and autophagy. We next adapted this technology to conduct a small molecule screen and identified compounds that altered the intracellular accumulation of the human aggregation prone mutant that causes liver disease in α1-antitrypsin deficiency. This study provides powerful validation for advancement in preclinical drug discovery campaigns by screening live C. elegans modeling α1-antitrypsin deficiency and other complex disease phenotypes on high-content imaging platforms
Anti-Biofilm Compounds Derived from Marine Sponges
Bacterial biofilms are surface-attached communities of microorganisms that are protected by an extracellular matrix of biomolecules. In the biofilm state, bacteria are significantly more resistant to external assault, including attack by antibiotics. In their native environment, bacterial biofilms underpin costly biofouling that wreaks havoc on shipping, utilities, and offshore industry. Within a host environment, they are insensitive to antiseptics and basic host immune responses. It is estimated that up to 80% of all microbial infections are biofilm-based. Biofilm infections of indwelling medical devices are of particular concern, since once the device is colonized, infection is almost impossible to eliminate. Given the prominence of biofilms in infectious diseases, there is a notable effort towards developing small, synthetically available molecules that will modulate bacterial biofilm development and maintenance. Here, we highlight the development of small molecules that inhibit and/or disperse bacterial biofilms specifically through non-microbicidal mechanisms. Importantly, we discuss several sets of compounds derived from marine sponges that we are developing in our labs to address the persistent biofilm problem. We will discuss: discovery/synthesis of natural products and their analogues—including our marine sponge-derived compounds and initial adjuvant activity and toxicological screening of our novel anti-biofilm compounds
Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms
Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials—skeletal muscle, tendons and plant tissues—and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.</p
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