324,978 research outputs found
Stroke onset time determination using MRI relaxation times without non-ischaemic reference in a rat stroke model
The correlation of plasma proteins binding capacity and flavopiridol cellular and clinical trial studies
Optical imaging spectroscopy
During the recent solar maximum the combination of imaging and spectroscopy in the visible part of the spectrum became a powerful tool for observational study of flares primarily because of the development of two-dimensional charge-coupled-device (CCD) arrays. In combination with appropriate new operational methods, this has led to the ability to observe, for the first time, the preflare and impulsive-phase physical processes associated with spatially resolved features of flare loops. As a result of concurrent theoretical developments, modeling progressed from an empirical to a physical level. This made it possible to interpret imaging spectra in terms of coronal pressure and heat flux, particle beam heating, chromospheric evaporation, and explosive chromospheric dynamics at the footpoints of flare loops. There is clear potential for further advances in the near future, taking advantage of improvements in digital recording speed (approx. 10-fold), number of photosensitive elements per array (approx. 10-fold), real-time data pre-reduction (potentially 10- to 100-fold), and using multiple CCD arrays. By the time of the next solar maximum imaging spectroscopy is expected to achieve spatial resolution or approx. arc 1 arc s, temporal resolution or approx. 5 s, and simultaneous critically-sampled spectroscopy of several lines and continua. As a result, continued increase in our understanding of the physical processes and configurations of solar flares in the chromosphere, temperature minimum region, and photosphere can be anticipated. Even greater progress toward a more global understanding of flares will obviously come about when simultaneous optical, X-ray, and gamma-ray imaging spectroscopy are possible
Stellar populations -- the next ten years
The study of stellar populations is a discipline that is highly dependent on
both imaging and spectroscopy. I discuss techniques in different regimes of
resolving power: broadband imaging (R~4), intermediate band imaging (R~16, 64),
narrowband spectral imaging (R~256, 1024, 4096). In recent years, we have seen
major advances in broadband all-sky surveys that are set to continue across
optical and IR bands, with the added benefit of the time domain, higher
sensitivity, and improved photometric accuracy. Tunable filters and integral
field spectrographs are poised to make further inroads into intermediate and
narrowband imaging studies of stellar populations. Further advances will come
from AO-assisted imaging and imaging spectroscopy, although photometric
accuracy will be challenging. Integral field spectroscopy will continue to have
a major impact on future stellar population studies, extending into the near
infrared once the OH suppression problem is finally resolved. A sky rendered
dark will allow a host of new ideas to be explored, and old ideas to be
revisited.Comment: Invited review, IAUS 241, "Stellar Populations as Building Blocks of
Galaxies," eds. Vazdekis, Peletier. 12 pages, 1 table. (The sideways table
should print ok; there are 10 columns.
Cometary spectroscopy and imaging
The objective is to investigate the spectroscopic and morphological characteristics of comets and selected minor planets over a wide range of heliocentric distances as they may suggest or constrain models of cometary processes, their formation environments and evolution. Direct images of all observable comets and 300-800 nm spectra of the brighter ones are obtained on a monthly basis with a charge coupled device spectrograph-camera. The direct images may be used for astrometry, photometry, and studies of coma and tail morphology. In some cases, anisotropic dust emission can provide information on the nucleus spin vector. Spectra may provide data on strengths of the principle emission for comparison of gas/dust ratios of a large sample of comets. Long integrations of minor planets in comet-like and nearby orbits are made to search for faint comae
Single-object Imaging and Spectroscopy to Enhance Dark Energy Science from LSST
Single-object imaging and spectroscopy on telescopes with apertures ranging
from ~4 m to 40 m have the potential to greatly enhance the cosmological
constraints that can be obtained from LSST. Two major cosmological probes will
benefit greatly from LSST follow-up: accurate spectrophotometry for nearby and
distant Type Ia supernovae will expand the cosmological distance lever arm by
unlocking the constraining power of high-z supernovae; and cosmology with time
delays of strongly-lensed supernovae and quasars will require additional
high-cadence imaging to supplement LSST, adaptive optics imaging or
spectroscopy for accurate lens and source positions, and IFU or slit
spectroscopy to measure detailed properties of lens systems. We highlight the
scientific impact of these two science drivers, and discuss how additional
resources will benefit them. For both science cases, LSST will deliver a large
sample of objects over both the wide and deep fields in the LSST survey, but
additional data to characterize both individual systems and overall systematics
will be key to ensuring robust cosmological inference to high redshifts.
Community access to large amounts of natural-seeing imaging on ~2-4 m
telescopes, adaptive optics imaging and spectroscopy on 8-40 m telescopes, and
high-throughput single-target spectroscopy on 4-40 m telescopes will be
necessary for LSST time domain cosmology to reach its full potential. In two
companion white papers we present the additional gains for LSST cosmology that
will come from deep and from wide-field multi-object spectroscopy.Comment: Submitted to the call for Astro2020 science white paper
A holistic multimodal approach to the non-invasive analysis of watercolour paintings
A holistic approach using non-invasive multimodal imaging and spectroscopic techniques to study the materials (pigments, drawing materials and paper) and painting techniques of watercolour paintings is presented. The non-invasive imaging and spectroscopic techniques include VIS-NIR reflectance spectroscopy and multispectral imaging, micro-Raman spectroscopy, X-ray fluorescence spectroscopy (XRF) and optical coherence tomography (OCT). The three spectroscopic techniques complement each other in pigment identification. Multispectral imaging (near infrared bands), OCT and micro-Raman complement each other in the visualisation and identification of the drawing material. OCT probes the microstructure and light scattering properties of the substrate while XRF detects the elemental composition that indicates the sizing methods and the filler content . The multiple techniques were applied in a study of forty six 19th century Chinese export watercolours from the Victoria & Albert Museum (V&A) and the Royal Horticultural Society (RHS) to examine to what extent the non-invasive analysis techniques employed complement each other and how much useful information about the paintings can be extracted to address art conservation and history questions
Near infrared imaging spectroscopy of NGC1275
We present H and K band imaging spectroscopy of the core regions of the
cD/AGN galaxy NGC1275. The spectra, including lines from H2, H, 12CO bandheads,
[FeII], and [FeIII], are exploited to constrain the star formation and
excitation mechanisms in the galaxy's nucleus. The near-infrared properties can
largely be accounted for by ionized gas in the NLR, dense molecular gas, and
hot dust concentrated near the active nucleus of NGC1275. The strong and
compact H2 emission is mostly from circumnuclear gas excited by the AGN and not
from the cooling flow. The extended emission of latetype stars is diluted in
the center by the thermal emission of hot dust.Comment: 16 pages, LaTex, 15 gif figures, aa.cls required, accepted for A&A,
high resolution images at http://astro1.ws.ba.dlr.d
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