The understanding of the solar outer atmosphere requires a simultaneous combination of imaging and spectral observations concerning the far UV lines that arise from the high chromospheres up to the corona. These observations must be performed with enough spectral, spatial and temporal resolution to reveal the small atmospheric structures and to resolve the solar dynamics. An Imaging Fourier Transform Spectrometer working in the far-UV (IFTSUV, Figure 1) is an attractive instrumental solution to fulfill these requirements. However, due to the short wavelength, to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR) requires a high optical surface quality and a very accurate (linear and angular) metrology to maintain the optical path difference (OPD) during the entire scanning process by: optical path difference sampling trigger; and dynamic alignment for tip/tilt compensation (Figure 2).
In the 2010 horizon, solar space missions such as LYOT and Solar Orbiter will allow high cadence UV observations of the Sun at spatial and spectral resolution never obtained before. To reach these goals, the two missions could take advantage of spectro-imagers. A reflective only optical solution for such an instrument is described in this paper and the first results of the mock-up being built at IAS are shown.
SPICE is a high resolution imaging spectrometer operating at extreme ultraviolet wavelengths, 70.4 – 79.0 nm and 97.3 -
104.9 nm. It is a facility instrument on the Solar Orbiter mission. SPICE will address the key science goals of Solar
Orbiter by providing the quantitative knowledge of the physical state and composition of the plasmas in the solar
atmosphere, in particular investigating the source regions of outflows and ejection processes which link the solar surface
and corona to the heliosphere. By observing the intensities of selected spectral lines and line profiles, SPICE will derive
temperature, density, flow and composition information for the plasmas in the temperature range from 10,000 K to
10MK. The instrument optics consists of a single-mirror telescope (off-axis paraboloid operating at near-normal
incidence), feeding an imaging spectrometer. The spectrometer is also using just one optical element, a Toroidal Variable
Line Space grating, which images the entrance slit from the telescope focal plane onto a pair of detector arrays, with a
magnification of approximately x5. Each detector consists of a photocathode coated microchannel plate image
intensifier, coupled to active-pixel-sensor (APS). Particular features of the instrument needed due to proximity to the Sun
include: use of dichroic coating on the mirror to transmit and reject the majority of the solar spectrum, particle-deflector
to protect the optics from the solar wind, and use of data compression due to telemetry limitations.
The spectroscopy of the far UV emission lines of the solar spectrum combined with an imaging capability is essential to
understand the physics of the outer solar atmosphere. An imaging Fourier transform spectrometer (IFTSUV) is an
attractive instrumental solution to perform such far-UV solar observations. Working in the far UV involves high
precision metrology to maintain the optical path difference (OPD) during the entire scanning process of the
interferogram. It also involves a compact all-reflection design for UV applications. We present the specification of a
servo-system that enables dynamic tip/tilt alignment compensation and OPD sampling measurement of the IFTSUV
scanning mirror. We also discuss the first experimental results of a breadboard as well as the preliminary design of a
space-based device.
Imaging Fourier Transform Spectrometer working in the far UV (IFTSUV) may be the technical solution to
answer many unsolved problems concerning the physics of the solar outer atmosphere. The VUV domain
highly constrains the instruments design and performances as it demands a high optics surface quality and an
accurate metrology to preserve IFTSUV spectral precision and Signal to Noise Ratio (SNR). We present the
advancements on the specification of a metrology system, meeting the predicted performance requirements of
an IFTSUV.
Our purpose is to test if Pluronic® fluorescent nanomicelles can be used for in vivo two-photon imaging of both the normal and the tumor vasculature. The nanomicelles were obtained after encapsulating a hydrophobic two-photon dye: di-stryl benzene derivative, in Pluronic block copolymers. Their performance with respect to imaging depth, blood plasma staining, and diffusion across the tumor vascular endothelium is compared to a classic blood pool dye Rhodamin B dextran (70 kDa) using two-photon microscopy. Pluronic nanomicelles show, like Rhodamin B dextran, a homogeneous blood plasma staining for at least 1 h after intravenous injection. Their two-photon imaging depth is similar in normal mouse brain, using 10 times less injected mass. In contrast with Rhodamin B dextran, no extravasation is observed in leaky tumor vessels due to their large size: 20-100 nm. In conclusion, Pluronic nanomicelles can be used as a blood pool dye, even in leaky tumor vessels. The use of Pluronic block copolymers is a valuable approach for encapsulating two-photon fluorescent dyes that are hydrophobic and not suitable for intravenous injection.
The study of the outer solar atmosphere requires combining imaging and spectroscopy in the UV lines formed
in the high chromosphere, the transition region and the corona. We start from the science requirements and we
define the instrumental specifications in terms of field-of-view (FOV), spatial, temporal and spectral resolution
and bandpass. We propose two different all-reflection optical architectures based on interferometric techniques:
Spatial Heterodyne Spectroscopy (SHS); and Imaging Transform Spectrometer (IFTS). We describe the different
set-ups and compare the potential performances of the two types of solutions, and discuss their feasibility. We
conclude that IFTS appears to be the best solution, meeting the needs of UV solar physics. However, we point
out the many difficulties to be encountered, especially as far as metrology is concerned.
Multiphoton microscopy has shown a powerful potential for biomedical in vivo and ex vivo analysis of tissue sections
and explants. Studies were carried out on several animal organs such as brain, arteries, lungs, and kidneys. One of the
current challenges is to transfer to the clinic the knowledge and the methods previously developed in the labs at the
preclinical level.
For tumour staging, physicians often remove the lymph nodes that are localized at the proximity of the lesion. In case of
breast cancer or melanoma, sentinel lymph node protocol is performed: pathologists randomly realize an extensive
sampling of formol fixed nodes. However, the duration of this protocol is important and its reliability is not always
satisfactory.
The aim of our study was to determine if multiphoton microscopy would enable the fast imaging of lymph nodes on
important depths, with or without exogenous staining. Experiments were first conducted on pig lymph nodes in order to
test various dyes and to determine an appropriate protocol. The same experiments were then performed on thin slices of
human lymph nodes bearing metastatic melanoma cells. We obtained relevant images with both endofluorescence plus
second-harmonic generation and xanthene dyes. They show a good contrast between tumour and healthy cells.
Furthermore, images of pig lymph nodes were recorded up to 120μm below the surface. This new method could then
enable a faster diagnosis with higher efficiency for the patient. Experiments on thicker human lymph nodes are currently
underway in order to validate these preliminary results.
KEYWORDS: In vivo imaging, Blood brain barrier, Brain, Blood, Neurons, Neuroimaging, Two photon excitation microscopy, Plasma, Two photon imaging, Tissues
Staining and imaging glial cells in vivo while observing the microvasculature could help understand brain physiology, namely neuronal-glial-vascular communication. Two-photon excitation microscopy provides a means to monitor these interactions at the cellular level in living animals, but the cells of interest must be fluorescent. Injecting dyes intravenously is a rapid and quasi noninvasive method to stain cells in the brain. It necessitates that the dye is soluble in the blood plasma and crosses the blood brain barrier (BBB). We demonstrate here, using two-photon imaging, that sulforhodamine B (SRB) crosses the BBB and stains in vivo, specifically mouse astrocytes. This is confirmed by experiments on primary neurons and astrocytes cultures showing the preferential SRB staining of the latter. SRB is rapidly eliminated from the blood, which allows repeated injections in longitudinal studies.
Since the early nineties, multiphoton microscopy has become a powerful tool to investigate morphological and
physiological parameters in vivo or on thick ex vivo sections. To stain structures of interest many dyes have been developed and two-photon properties (cross section, excitation and
emission spectra) of existing ones have been characterized.
Recently, our team has shown a new property of sulforhodamine B (SRB). This dye has the ability to bind specifically
elastic fibers. The observation of elastin using its endofluorescence properties was already widely described but required
long exposition delays up to 10s and the imaging depth was limited to approximately 50 μm. With a multiphoton microscope and SRB, it is possible to observe elastic fibers directly in the living animal or on thick tissue sections with a micrometric spatial resolution in less than one second per image with an imaging depth of ~ 200
μm. Moreover, with an appropriate set of filters, we can acquire simultaneously the SRB and the second harmonic generation (SHG) signals of collagen fibers. Here, we report various applications of this new staining method on different arterial rings. The layers of the arterial wall, as well as, the elastic lamellae are observed and are numbered. With the addition of a nuclear stain such as the Hoechst 33342, a more accurate morphological study of the arterial walls can be accomplished. Finally, an intravital observation of the saphenous artery morphology is presented.
Brain pathologies, including stroke and tumors, are associated with a variable degree of breakdown of the blood-brain barrier (BBB), which can usefully be studied in animal models. We describe a new optical technique for quantifying extravasation in the cortex of the living mouse and for imaging intraparenchymal tissue. Leakiness of the BBB was induced by microbeam x-irradiation. Two fluorescent dyes were simultaneously infused intravenously, one of high molecular weight (fluorescein-labeled dextran, 70 kDa, green fluorescence) and one of low molecular weight (sulforhodamine B, 559 Da, red fluorescence). A two-photon microscope, directed through a cranial window, obtained separate images of the two dyes in the cortex. The gains of the two channels were adjusted so that the signals coming from within the vessels were equal. Subtraction of the image of the fluorescein-dextran from that of the sulforhodamine B gave images in which the vasculature was invisible and the sulforhodamine B in the parenchyma could be imaged with high resolution. Algorithms are presented for rapidly quantifying the extravasation without the need for shape recognition and for calculating the permeability of the BBB. Sulforhodamine B labeled certain intraparenchymal cells; these cells, and other details, were best observed using the subtraction method.
Until now, the imaging of elastic fibers was restricted to tissue sections using the endofluorescence properties of elastin or histological dyes. Methods to study their morphology in vivo and in situ have been lacking. We present and characterize a new application of a fluorescent dye for two-photon microscopy: sulforhodamine B (SRB), which is shown to specifically stain elastic fibers in vivo. SRB staining of elastic fibers is demonstrated to be better than using elastin endofluorescence for two-photon microscopy. Our imaging method of elastic fibers is shown to be suitable for simultaneous imaging with both other fluorescent intravital dyes and second-harmonic generation (SHG). We illustrate these findings with intravital imaging of elastic and collagen fibers in muscle epimysium and endomysium and in blood vessel walls. We expect SRB staining to become a key method to study elastic fibers in vivo.
SMESE (SMall Explorer For the study of Solar Eruptions) is a Franco-Chinese microsatellite mission. The scientific
objectives of SMESE are the study of coronal mass ejections and flares. Its payload consists of three instrument
packages : LYOT, DESIR and HEBS. LYOT is composed of a Lyman α (121.6 nm) coronagraph, a Lyman α disk imager and a far UV disk imager. DESIR is an infrared telescope working at 35 μm and 150 μm. HEBS is
a high energy burst spectrometer working in X rays and γ rays covering the 10 keV to 600 MeV range. SMESE
will be launched around 2011, providing a unique opportunity of detecting and understanding eruptions at the
maximum activity phase of the solar cycle in a wide range of energies. The instrumentation on board SMESE is
described in this paper.
The study of the Sun in the UV spectral domain is essential for a better understanding of the physical processes
taking place in the solar atmosphere. The main tools for this study are imagers and spectrometers. Nevertheless,
the analysis of imagery data is rapidly limited unless spectral information is available, and the association of
spectrometers and imagers is limited by the lack of coherence between the instruments. Therefore, the design of
an imaging spectrometer in UV is a priority for solar physicists. In the far UV, only all reflective optical systems
can be used thus an imaging Fourier transform spectrometer (IFTS) is the ideal candidate for the realization of
such an instrument. The performances of an IFTS are given by the modulation efficiency. Theoretical study of
performances and scientific objectives lead to technical and operating specifications. A mock-up of an IFTSUV
has been built at IAS to validate the working principle. Its optical design and alignment are described in this
paper. The first results are shown and discussed. Planned modifications of the design are also discussed.
Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. The diffraction fringe from the occulter and the vignetted pupil which degrades the spatial resolution prevent observing the inner corona inside typically 2-2.5 solar radii. Formation flyers open new perspectives and allow to conceive giant, externally-occulted coronagraphs using a two-component space system with the external occulter on one spacecraft and the optical instrument on the other spacecraft at approximately 100 m from the first one. ASPICS (Association de Satellites Pour l'Imagerie Coronographique Solaire) is a mission proposed to CNES in the framework of their demonstration program of formation flyers which is presently under study to exploit this technique for coronal observations. In the baseline concept, ASPICS includes three coronagraphs operating in three spectral domains: the visible continuum (K-corona brightness), the HI Lyman alpha emission line at 121.6 nm, and the HeII emission line at 30.4 nm. Their unvignetted fields of view extend from 1.1 to 3.2 solar radii with a typical spatial resolution of 3 arcsec. In order to connect coronal activity to photospheric events, ASPICS further includes two disk imagers. The first one is devoted to the HI Lyman alpha emission line. The second one is a multi-channel instrument similar to SOHO/EIT and devoted to the HeII (30.4 nm), FeIX/X (17.1 nm) and FeXII (19.5 nm) emission lines. Two concepts of the space system are under consideration: a symmetric configuration where the disk imagers and the external occulter are on one spacecraft and the coronagraphs on the other, an asymmetric configuration where the external occulter is on one spacecraft and the scientific instruments are regrouped on the other one.
Knowledge of the volume of blood per unit volume of brain tissue is important for understanding brain function in health and disease. We describe a novel method using two-photon laser scanning microscopy to obtain the local blood volume in the cortex of the anesthetized mouse. We infused fluorescent dyes in the circulating blood and imaged the blood vessels, including the capillaries, to a depth of 400 microns below the dura at the brain surface. Blood volume was calculated by normalizing the total fluorescence measured at each depth. This method, which dispenses with form recognition, is rapid and only weakly sensitive to background noise; it could be extended to measure the leakiness of the blood vessels.
The LYOT (LYman Orbiting Telescope) solar mission (proposed for a CNES micro-satellite) is composed of a disk imager and a coronagraph, both working at Lyman-α (121.6 nm). The coronagraph is internally occulted and all-reflective with a field-of-view of 1.2 R up to 2.5 R and high spatial resolution (2 pixels) amounts to 5 arcsec. The optical design is driven by the requirement to use a superpolished spherical mirror to minimize the scattered light into the instrument. The LYOT mission will observe the Lyman-α corona at high cadence (1 image/5 minutes) over a period of two years.
The LYOT (LYman Orbiting Telescope) solar mission is proposed to be implemented on a micro-satellite of CNES (France) under phase A study. It includes two main instruments, which image the solar disk and the low corona up to 2.5 Ro in the H I Lyman-α line at 121.6 nm. The spatial resolution is about 1” for the disk and 2.5” for corona. It also carries an EIT-type telescope in the He II (30.4 nm) line. The coronagraph needs a super polished mirror at the entrance pupil to minimize the light scattering. Gratings and optical filters are used to select the Lyman-α wavelength. VUV cameras with 2048×2048 pixels record solar images up to every 10 seconds.
The satellite operates at a high telemetry rate (more then 100 kb/s, after onboard data compression). The envisaged orbits are either geostationary or heliosynchronous. Possible launch dates could be end of 2006 - beginning of 2007.
Bernhard Fleck, E. Marsch, Ester Antonucci, Peter Bochsler, J. Bougeret, R. Harrison, R. Marsden, M. Coradini, Oscar Pace, Rainer Schwenn, Jean-Claude Vial
The key mission objective of the Solar Orbiter is to study the Sun from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar rotation in order to examine the solar surface and the space above from a co-rotating vantage point at high spatial resolution. Solar Orbiter will also provide images of the Sun's polar regions from heliographic latitudes as high as 38 degrees. The strawman payload encompasses two instrument packages: Solar remote-sensing instruments: EUV full-sun and high resolution imager, high-resolution EUV spectrometer, high-resolution and full-sun visible light telescope and magnetograph, EUV and visible-light coronagraphs, radiometers. Heliospheric instruments: solar wind analyzer, radio and plasma wave analyzer, magnetometer, energetic particle detectors, interplanetary dust detector, neutral particle detector, solar neutron detector. To reach its novel orbit, Solar Orbiter will make use of low-thrust solar electric propulsion (SEP) interleaved by Earth and Venus gravity assists. Solar Orbiter was selected by ESA's Science Programme Committee (SPC) in October 2000 as a Flexi-mission, to be implemented after the BepiColombo cornerstone mission to Mercury before 2013. This paper summarizes the science to be addressed with the Solar Orbiter, followed by brief descriptions of the strawman payload, the mission profile, and the spacecraft and ground segment designs.
The instrument SUMER (solar ultraviolet measurements of emitted radiation) is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 multiplied by 106 K and above. The observations will be performed, on board SOHO (solar and heliospheric observatory) scheduled for launch in November 1995, by a scanning, normal-incidence telescope/spectrometer system in the wavelength range from 500 to 1610 angstrom. Spatial resolution requirements compatible with the pointing stability of SOHO are less than 1000 km corresponding to about 1-arcsec angular resolution. Doppler observations of EUV line shifts and broadenings should permit solar plasma velocity measurements down to 1 km s-1. We report here on some specific features of this instrument related to its pointing as well as its spatial and spectral resolution capabilities.
In this paper a summary of recent work on proton tunneling in intermolecular hydrogen bonds in the condensed phase is presented and its relevance to biological systems is discussed. Dye molecules are used to influence the proton structure in neighboring hydrogen bonds. The optical transitions of the dye serve as a probe of this structure and the dynamics. A variety of optical spectroscopic measurements at low temperatures leads to a determination of the tunneling splitting and the rate of proton transfer in benzoic acid dimers. A theoretical analysis of these data within a simplified model suggests that fluctuadons of the energy difference of the tautomers determine the relaxation behavior and that multiphonon processes dominate the relaxation of delocalized protons. 1.
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