176 research outputs found

    Measuring radon in soil gas and groundwaters: a review

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    Instruments for the measurements of radon and its decay products in earthquake research are based mostly on the detection of alpha particles. The devices and methods used depend on whether the techniques measure radon or radon decay products, and the duration of the measurements, of which there are three types: i) grab or instantaneous, ii) integrating and iii) continuous. Other criteria used in the design of these instruments are field measurements applicability, portability, convenience and reliability. With the recent increased demand for radon and radon decay products measurements, instruments development has focused on the design of appropriate devices for short-term measurements, as well as on more complex and sophisticated instruments for long-term measurements used in radon research for geophysical, geochemical and hydrological studies

    Multimodality Imaging Of Torpedo Maculopathy With Swept-Source, En Face Optical Coherence Tomography And Optical Coherence Tomography Angiography.

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    PURPOSE: Multimodality image analysis of two cases of torpedo maculopathy. METHODS: Imaging with fundus photography, autofluorescence (AF), swept-source optical coherence tomography (OCT), en face OCT, and OCT angiography. RESULTS: The basal diameter of the torpedo lesions was 1 mm Ă— 2 mm. One case had a satellite lesion. Autofluorescence indicated variable loss of signal. Swept-source OCT and en face OCT demonstrated fundus excavation, attenuation of nuclear layers and disruption of the outer plexiform layer, loss of photoreceptors and a subretinal cleft. In one case, Sattler layer appeared extended at the cleft. Optical coherence tomography angiography indicated loss of flow in deep retinal vessels and increased flow in choroidal vessels surrounding the cleft. CONCLUSION: Multimodal imaging findings of torpedo maculopathy include disruption of the deep retinal capillary network, expansion of Sattler layer, and increased signal around the subretinal cleft

    Deep stratosphere-to-troposphere transport (STT) over SE Europe: a complex case study captured by enhanced <sup>7</sup>Be concentrations at the surface of a low topography region

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    International audienceIn this study we present a complex case study of a Stratosphere-to-Troposphere Transport (STT) event down to the surface of a low topography region in Northern Greece, during the second fortnight of March 2000. During this event our surface station at Livadi (23°15 E/40°32 N, 850 m a.s.l.), was influenced by very different synoptic systems developing over Eastern Europe, N. America and the N. Atlantic, the last one evolving to a cut-off low over France/Spain. This is the first study, to our knowledge, that presents a down to the surface STT event in the eastern Mediterranean. The intrusion is primarily captured with the use of the cosmogenic radionuclide 7Be, which increased to 9.07 mBq m-3 and 9.37 mBq m-3 on 30 and 31 March 2000, respectively. A 7Be concentration of around 8 mBq m-3 recorded during parallel measurements at Thessaloniki (20 m a.s.l.) gives strong evidence that air of stratospheric origins has even gone down to sea level. A rapid increase of 10?15 ppb is also observed in the surface ozone concentration on 31 March 2000. The relative increase of both tracers is consistent with a volume fraction of stratospheric air at the surface of about 5%, but the substantial increase in 7Be flags more clearly the event. Trajectory analyses, in conjunction with the evolution of the synoptic situation described by potential vorticity maps, are used for the exact identification of the different intrusions and the attribution of each intruding parcel of stratospheric air to a certain filament of high PV. Finally, the persistency of the stratospheric layers in the troposphere is another interesting point of this case study. The vast majority of the trajectories spent 7?10 days in the troposphere before reaching the surface at Livadi station

    Radon measurements along active faults in the Langadas Basin, northern Greece

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    A network of three radon stations has been established in the Langadas Basin, northern Greece for radon monitoring by various techniques in earthquake prediction studies. Specially made devices with plastic tubes including Alpha Tracketch Detectors (ATD) were installed for registering alpha particles from radon and radon decay products exhaled from the ground, every 2 weeks, by using LR-115, type II, non-strippable Kodak films, starting from December 1996. Simultaneous measurements started using Lucas cells alpha spectrometer for instantaneous radon measurements in soil gas, before and after setting ATDs at the radon stations. Continuous monitoring of radon gas exhaling from the ground started from the middle of August 1999 by using silicon diode detectors, which simultaneously register meteorological parameters, such as rainfall, temperature and barometric pressure. The obtained data were studied together with the data of seismic events, such as the magnitude, <i>M<sub>L</sub></i>, of earthquakes that occurred at the Langadas Basin during the period of measurements, as registered by the Laboratory of Geophysics, Aristotle University of Thessaloniki, in order to find out any association between them

    Radon measurements in association with earthquakes

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    A network of three radon stations has been established in the Langadas basin, North Greece. Newly made devices with plastic tubes are in operation with a-particle track detectors (ATDs) in registering a-particles from radon and radon decay products exhaled from the ground, every two weeks, starting from December 1996, by using LR-115, type II, nonstrippable Kodak films. Simultaneous measurements are made by using Lucas a-scintillation cells for instantaneous measurements of radon in soil gas, before and after setting the ATDs at the radon stations. The new devices used have the advantage of not using heating systems nor electrical power in the nearby area of the stations. Radon flux registrations ranged between 507 and 85880 tr cm22 or 1.5 and 188.9 tr cm22 h21, in the period of measurement, while radon concentrations in soil gas ranged between 528 and 35095 Bq m23 at the same time

    Radon measurements along active faults in the Langadas Basin, northern Greece

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    Detection of extrascleral extension in uveal melanoma with histopathological correlation

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    PURPOSE: Uveal melanoma is the most common primary intraocular malignancy. Extrascleral extension (ESE) is rare, but associated with an increased rate of orbital recurrence and an overall poor prognosis. Clinical studies show low rates when compared with histological studies. Due to the prognostic importance of ESE, we sought to compare our clinical, intraoperative, and histological detection rates. DESIGN: A retrospective cross-sectional case series. METHODS: A list of eyes enucleated for uveal melanoma was compiled from the admissions records of the London Ocular Oncology Service during the 28-month period, i.e. January 2010-April 2012. The surgical and clinical notes of patients with histopathology proven ESE were reviewed to determine when it was first diagnosed or suspected. The subsequent management of these cases is discussed. RESULTS: A total of 16 out of 174 (9%) eyes had histologically proven ESE. Eight of 16 cases were detected preoperatively at clinical examination, including the use of ocular ultrasound, 3 of 16 were discovered intra-operatively, and 5 of 16 deemed microscopic ESE, were first detected on histological examination. Seven of 7 (100%) of cases with anterior ESE were detected clinically by slit lamp biomicroscopy, while only 1 out of 9 (11%) of cases with posterior ESE was detected preoperatively with ultrasound. CONCLUSIONS: Slit lamp biomicroscopy is sensitive for detecting anterior ESE. Most posterior ESE is microscopic, but macroscopic posterior ESE may also be missed by B-scan ocular ultrasound. Orbital surgeons should be suspicious of clinically undetected posterior ESE, and consider adjuvant orbital radiotherapy in cases with macroscopic ESE
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