Light interaction with live cells can lead to important effects. Near infrared (NIR) lasers are used in therapies to diminish inflammation and pain. In a microscopic scale, NIR laser light has been used to stimulate and guide the growth of cells like neurons and fibroblasts. However, it is still unclear what NIR laser radiation provokes to the cells at the molecular and biophysical levels. In this contribution we report the effects of a continuous wave 810-nm laser on the plasma membrane of in vivo 3T3 fibroblast cells. Membranes were labelled the lipophilic styryl dye FM 4-64 and imaged by confocal microscopy. We found that the NIR laser produces an increase of the fluorescence intensity at the location of laser spot. This intensity boost vanishes when the laser is turned off. The time taken by the increase and decrease is of the order of 10 seconds. The mean fluorescence increase, calculated over 75 independent measurements, equals 19%. The experiments reveal that the fluorescence rise is a growing function of the laser power. This dependence is well fitted with a square root function. The NIR laser provokes a rise in the number of molecular associations dye-lipid. The results reported here may be a consequence of a combination of induced increments in membrane fluidity and exocytosis. To the best of our knowledge, this is the first demonstration of the influence of focused NIR laser on the lipid dynamics of a live cell plasma membrane.
Optical tweezers constitute an increasingly used tool for the study of biomechanical properties of cells. Here we report experiments for the projection induction of NIH3T3 fibroblast cells, using a single-trap optical tweezers. The system is based on a 1064-nm, 50mW infrared gaussian laser beam, a 100x microscope objective with 1.25 numerical aperture and a temperature-controlled warming plate to maintain cell viability. Eighteen cells were exposed to the focussed laser beam in different cell zones and another 18 cells were observed without laser stimulation as a control population. The results show that the probability of lamelipodia growth increases on exposed cells by a factor 1.5.
The 'Imaka project is a high-resolution wide-field imager proposed for the Canada-France-Hawaii telescope
(CFHT) on Mauna Kea. 'Imaka takes advantage of two features of the optical turbulence above Mauna Kea:
weak optical turbulence in the free-atmosphere and boundary layer turbulence which is highly confined within a
surface layer tens of meters thick and or the telescope enclosures. The combination of the two allows a groundlayer
adaptive optics system (GLAO) to routinely deliver an extremely-wide corrected field of view of one-degree
at an excellent free-atmosphere seeing limit at visible wavelengths. In addition, populating the focal-plane with
orthogonal-transfer CCDs provides a second level of image improvement on the free-atmosphere seeing and the
residual GLAO correction. The impact of such an instrument covers a broad range of science and is a natural
progression of CFHT's wide-field expertise.
We have made high order (32x32 subaperture) Shack-Hartmann wavefront sensor observations of binary stars
with separations of approximately 20 arcseconds using the University of Hawaii 2.2 m telescope. We present
preliminary results of a Slope Detection and Ranging (SLODAR) analysis of the data yielding measurements of
turbulence strength, wind velocity and velocity dispersion as a function of altitude, with approximately 500 m
vertical resolution. The aim of the investigation is to explore the validity of the Taylor frozen flow approximation
and the implications for layer-oriented predictive AO reconstruction algorithms.
We describe the current status of the SLODAR optical turbulence monitors, developed at Durham University, for support
of adaptive optics for astronomy. SLODAR systems have been installed and operated at the Cerro Paranal and Mauna
Kea observatories, and a third will be deployed at the South African Astronomical Observatory in 2008. The instruments
provide real-time measurements of the atmospheric turbulence strength, altitude and velocity. We summarize the
capabilities of the systems and describe recent enhancements. Comparisons of contemporaneous data obtained with
SLODAR, MASS and DIMM monitors at the ESO Paranal site are presented.
We present observations of the high-speed variations of the altitude of the telluric sodium layer. In this experiment we observed the Gemini-North sodium laser guide star from approximately 80 meters
off-axis using the UH-2.2m telescope on Mauna Kea, Hawaii. Observations were made using an electron-multiplying camera at a rate of about 100Hz. The temporal power spectrum of the layer centroid follows a power law between 0.001 and 1Hz and we find that the exponent of the power law (α=-1.8) is similar to that found at lower temporal frequencies from lidar experiments. This data set taken with the lidar results shows that the power spectrum of the sodium layer mean altitude follows a simple power law over 5 orders of magnitude from 10-4.5 Hz to 1Hz. The approach taken in this experiment is difficult due to telescope jitter in any of the three telescopes (Gemini-N, Gemini-N LGS launch telescope, or from the observing UH2.2m) and atmospheric tip/tilt wave front aberrations. We circumvented these problems by analyzing the differential motion between two distinct features that appeared in the sodium layer during that night.
We present the concept of an instrument for the monitoring of the optical turbulence in the first 300 meters above the ground with an altitude resolution of 10 meters approximately. The method is based on a modified version of the generalized scidar. It could be implemented with the use of a 40-cm telescope, a 1376x1040 pixels CCD detector with low readout noise at 20 frames per second, a fast commercial personal computer and a colimating optics. The ideal light source is a bright double star with an angular separation of 180". The principal difference from a conventional generalized scidar is that the scintillation images produced by each star would be fully separated on the detector, whereas in a generalized scidar, the images overlap over a certain region. The image processing consists of selecting on the detector two subframes containing each the scintillation image of one of the stellar component, recenter each image on the corresponding subframe (to correct for telescope missguiding and shaking), and compute the spatial correlation of the two subframes. This procedure is to be repeated several thousand times and the output is the mean correlation. The data reduction would be very similar to that of the generalized scidar, which consists of the inversion of a Fredholm integral equation. This method is particularly interesting to study the turbulence above locations that are a few hundred meters below a given site summit.
The Observatorio Astronomico Nacional at San Pedro Martir is situated on the summit of the San Pedro Martir Sierra in the Baja California peninsula of Mexico, at 2800m above sea level. For as long as three decades, a number of groups and individuals have gathered extremely valuable data leading to the site characterization for astronomical observations. Here we present a summary of the most important results obtained so far. The aspects covered are: weather, cloud coverage, local meteorology, atmospheric optical extinction, millimetric opacity, geotechnical studies, seeing, optical turbulence profiles, wind profiles and 3D simulations of atmospheric turbulence. The results place San Pedro Martir among the most favorable sites in the world for astronomical observations. It seems to be particularly well-suited for extremely large telescopes because of the excellent turbulence and local wind conditions, to mention but two characteristics. Long-term monitoring of some parameters still have to be undertaken. The National University of Mexico (UNAM) and other international institutions are putting a considerable effort in that sense.
The temporal fluctuations of the optical turbulence at different altitudes in the atmosphere are investigated. About 2400 C2N profiles, measured with a generalized scidar at the Observatorio Astronomico Nacional de San Pedro Martir, are used to determine the mean amplitude and characteristic time of the relative fluctuations of the optical turbulence in five atmospheric slabs. It is found that the saturation values of the relative fluctuations of the turbulence are 26%, 37%, 28% and 31% and the mean time for reaching 63% of these saturation values are 0.50, 0.20, 0.20 and 0.16 hours for the altitude slabs [2;4], [4;9], [9;16] and [16;21]km, respectively.
We present the design of and recent results from the Large Binocular Telescope (LBT) facility SCIDAR. To our knowledge, this work will produce the first SCIDAR designed as a user instrument for routine seeing measurements in support of telescope operations. Using a commercial, off-the-shelf approach, we have minimized the resources required for system construction.
We present the first simultaneous monitoring of the vertical distributions of the optical turbulence strength CN2(h) and the wind velocity V(h), along the whole optical path. For that purpose, a new algorithm has been developed for the analysis of the spatio-temporal correlation of scintillation images, obtained with the Generalized Scidar (GS). The algorithm allows for dome seeing identification. The new method has being applied to the GS data collected during four one-week runs uniformly distributed during 1998, for the characterization of Cerro Pachon, the Gemini South Telescope site. Comparison of V(h) obtained with the GS and instrumented balloons, respectively, gives a great deal of confidence in the new method. The analysis of the 6900 CN2(h) and V(h) profiles obtained, leads to a statistical study of the most important parameters relevant for the development of adaptive optical systems.
A detailed analysis of anisotropy in the point spread function (PSF) associated with off-axis adaptive astronomical correction is presented. The results obtained are based on the experimental Cn2 profile which has been recently measured at San Pedro Martir observatory (Mexico). It is found that the PSF has a complicated shape that depends strongly on the wavelength and on the separation between the guide and observed stars.
The efficiency of off-axis adaptive astronomical systems is estimated for four astronomical sites: Paranal (Chili), Roque de los Muchachos (Canary Islands), San Pedro Martir (Mexico) and Observatoire de Haute Provence (France). The efficiency of interest is considered through the Strehl ratio of the corrected image calculated for V, J and K bands and for 8-m class telescopes. The experimental optical turbulence strength Cn2(z) profiles necessary for calculations have been measured with balloon flights and with the Generalized Scidar. It is found that this efficiency depends mainly on the Cn2(z) profile layered structure and on the turbulence strength.
The effective wavefront outer scale L0 was monitored continuously during 16 nights in August-September 1997 using the new Grating Scale Monitor (GSM) instrument. Simultaneous comparison with the data form open-loop adaptive optics system on the ESO 3.6 m telescope revealed a good agreement of the L0 derived by both methods. The GSM principle is similar to the Shack-Hartmann sensor: angle of arrival fluctuations are measured with four 10-cm telescopes and the outer scale is computed from their normalized covariances. The seeing and effective wavefront velocity are measured as well. GSM does not suffer form dome and mirror seeing effects and can be used anywhere for site evaluation. Outer scale has log-normal distribution, its median is found to be 24 m, with a rms scatter of log L0 of +/- 0.22. Short isolated bursts of high L0 values were sometimes observed. A weak correlation of L0 and seeing angle exists for some nights. Decametric values of L0 found here imply that at baselines of few meters the influence of finite L0 on the energy balance between tip-tilt and higher-order modes must be properly taken into account. This can sensibly modify the predicted performance of adaptive optics systems.
We describe different works conducing to the adaptive optics system for the TIM 6.5m telescope. We show turbulence profiles result at our San Pedro Martir Observatory in Baja using the Generalized SCIDAR. We can conclude that the turbulence conditions in this site are comparable to the major observatories in the world. From these results and taken in account curvature AO simulations it is possible to predict the performances in limiting magnitude and sky coverage of different AO systems and telescopes in our observatory. We can also define the degree of the AO system for the TIM 6.5m telescope. We made a short description of our LOLA tip-tilt corrector system and the GUIELOA 19 elements curvature AO system. The calculation of the optics quality for the TIM 6.5m is briefly mentioned. Studies about the influence of the finite outerscale on the optical quality of AO corrected images are described.