Ultra-structural cell distribution of the melanoma marker iodobenzamide: improved potentiality of SIMS imaging in life sciences

BACKGROUND: Analytical imaging by secondary ion mass spectrometry (SIMS) provides images representative of the distribution of a specific ion within a sample surface. For the last fifteen years, concerted collaborative research to design a new ion microprobe with high technical standards in both mass and lateral resolution as well as in sensitivity has led to the CAMECA NanoSims 50, recently introduced onto the market. This instrument has decisive capabilities, which allow biological applications of SIMS microscopy at a level previously inaccessible. Its potential is illustrated here by the demonstration of the specific affinity of a melanoma marker for melanin. This finding is of great importance for the diagnosis and/or treatment of malignant melanoma, a tumour whose worldwide incidence is continuously growing. METHODS: The characteristics of the instrument are briefly described and an example of application is given. This example deals with the intracellular localization of an iodo-benzamide used as a diagnostic tool for the scintigraphic detection of melanic cells (e.g. metastasis of malignant melanoma). B16 melanoma cells were injected intravenously to C(57)BL(6)/J(1)/co mice. Multiple B16 melanoma colonies developed in the lungs of treated animals within three weeks. Iodobenzamide was injected intravenously in tumour bearing mice six hours before sacrifice. Small pieces of lung were prepared for SIMS analysis. RESULTS: Mouse lung B16 melanoma colonies were observed with high lateral resolution. Cyanide ions gave "histological" images of the cell, representative of the distribution of C and N containing molecules (e.g. proteins, nucleic acids, melanin, etc.) while phosphorus ions are mainly produced by nucleic acids. Iodine was detected only in melanosomes, confirming the specific affinity of the drug for melanin. No drug was found in normal lung tissue. CONCLUSION: This study demonstrates the potential of SIMS microscopy, which allows the study of ultra structural distribution of a drug within a cell. On the basis of our observations, drug internalization via membrane sigma receptors can be excluded

The variable finesse locking technique

Virgo is a power recycled Michelson interferometer, with 3 km long Fabry-Perot cavities in the arms. The locking of the interferometer has been obtained with an original lock acquisition technique. The main idea is to lock the instrument away from its working point. Lock is obtained by misaligning the power recycling mirror and detuning the Michelson from the dark fringe. In this way, a good fraction of light escapes through the antisymmetric port and the power build-up inside the recycling cavity is extremely low. The benefit is that all the degrees of freedom are controlled when they are almost decoupled, and the linewidth of the recycling cavity is large. The interferometer is then adiabatically brought on to the dark fringe. This technique is referred to as variable finesse, since the recycling cavity is considered as a variable finesse Fabry-Perot. This technique has been widely tested and allows us to reach the dark fringe in few minutes, in an essentially deterministic way

A Cross-correlation method to search for gravitational wave bursts with AURIGA and Virgo

We present a method to search for transient GWs using a network of detectors with different spectral and directional sensitivities: the interferometer Virgo and the bar detector AURIGA. The data analysis method is based on the measurements of the correlated energy in the network by means of a weighted cross-correlation. To limit the computational load, this coherent analysis step is performed around time-frequency coincident triggers selected by an excess power event trigger generator tuned at low thresholds. The final selection of GW candidates is performed by a combined cut on the correlated energy and on the significance as measured by the event trigger generator. The method has been tested on one day of data of AURIGA and Virgo during September 2005. The outcomes are compared to the results of a stand-alone time-frequency coincidence search. We discuss the advantages and the limits of this approach, in view of a possible future joint search between AURIGA and one interferometric detector.Comment: 11 pages, 6 figures, submitted to CQG special issue for Amaldi 7 Proceeding

Astrophysically Triggered Searches for Gravitational Waves: Status and Prospects

In gravitational-wave detection, special emphasis is put onto searches that focus on cosmic events detected by other types of astrophysical observatories. The astrophysical triggers, e.g. from gamma-ray and X-ray satellites, optical telescopes and neutrino observatories, provide a trigger time for analyzing gravitational wave data coincident with the event. In certain cases the expected frequency range, source energetics, directional and progenitor information is also available. Beyond allowing the recognition of gravitational waveforms with amplitudes closer to the noise floor of the detector, these triggered searches should also lead to rich science results even before the onset of Advanced LIGO. In this paper we provide a broad review of LIGO's astrophysically triggered searches and the sources they target

A simple line detection algorithm applied to Virgo data

International audienceWe propose a new method for the detection of spectral lines in random noise. It mimics the processing scheme of matching filtering, i.e., a whitening procedure combined with the measurement of the correlation between the data and a template. Thanks to the original noise spectrum estimate used in the whitening procedure, the algorithm can easily be tuned to various types of noise. It can thus be applied to the data taken from a wide class of sensors. This versatility and its small computational cost make this method particularly well suited for real-time monitoring in gravitational wave experiments. We show the results of its application to Virgo C4 commissioning data

A first study of environmental noise coupling to the Virgo interferometer

International audienceDuring the commissioning of the Virgo interferometer, a search for environmental noise contributions to the dark fringe signal was undertaken. Dedicated tests have been performed to identify major sources of disturbances and to understand the coupling mechanism with the interferometer. The major effect is due to seismic/acoustic noise coupling to the laser beam before the input mode cleaner, then propagating as beam power noise to the ITF dark fringe output signal. In this paper we illustrate the tests performed and preliminary results of our investigation

A first test of a sine-Hough method for the detection of pulsars in binary systems using the E4 Virgo engineering run data

Most of the known pulsars with frequencies lying in the best sensitivity range of the Virgo/LIGO/TAMA interferometers belong to binary systems. Accordingly their frequencies are Doppler shifted in an unknown way. We investigate a new method to search for and extract the parameters of such pulsars. A first preliminary test of this method, performed on the Virgo data recorded during the E4 engineering run, is presented

Data Acquisition System of the Virgo Gravitational Waves Interferometric Detector

International audienceVirgo is an experiment aiming at the detection of gravitational waves emitted by astrophysical sources. Its detector, based on a 3km arms interferometer, is a complex setup which requires several digital control loops running up to 10kHz, an accurate and reliable central timing system and an efficient data acquisition, all of them being distributed over 3km. We overview here the main hardware and software components developed for the data acquisition system (DAQ) and its current architecture. Then, we briefly discuss its connections with interferometer's controls, especially through the automation of the interferometer's startup procedure. Then, we describe the tools used to monitor the DAQ and the performances we measured with them. Finally, are described also the tools developped for the online detector monitoring, mandatory complement of the DAQ for the commissioning of the Virgo detector