A search for 4750- and 4765-MHz OH masers in Southern Star Forming Regions

We have used the Australia Telescope Compact Array (ATCA) to make a sensitive (5-$\sigma$ $\simeq$ 100 mJy) search for maser emission from the 4765-MHz $^2\Pi_{1/2}$ F=1$\to$0 transition of OH. Fifty five star formation regions were searched and maser emission with a peak flux density in excess of 100 mJy was detected toward fourteen sites, with ten of these being new discoveries. In addition we observed the 4750-MHz $^2\Pi_{1/2}$ F=1$\to$1 transition towards a sample of star formation regions known to contain 1720-MHz OH masers, detecting marginal maser emission from G348.550-0.979. If confirmed this would be only the second maser discovered from this transition. The occurrence of 4765-MHz OH maser emission accompanying 1720-MHz OH masers in a small number of well studied star formation regions has lead to a general perception in the literature that the two transitions favour similar physical conditions. Our search has found that the presence of the excited-state 6035-MHz OH transition is a much better predictor of 4765-MHz OH maser emission from the same region than is 1720-MHz OH maser emission. Combining our results with those of previous high resolution observations of other OH transitions we have examined the published theoretical models of OH masers and find that none of them predict any conditions in which the 1665-, 6035- and 4765-MHz transitions are simultaneously inverted. Erratum abstract: Dodson & Ellingsen (2002) included several observations with significant pointing errors, invalidating the upper limits found in these directions. These have now been reobserved or recalculated. A new table of upper limits has been generated, and two more masers that would have been seen have been found.Comment: Included an Erratum with Max as another author. This erratum was rejected by MNRAS (Feb 04) as it contained too much data. Resubmitted as a paper (Jun 04). Rejected (Sep 04) it had too little data. Resubmitted as reduced erratum (Apr 05). Still waitin

Infected lingual osseous choristoma : report of a case and review of the literature

Osseous choristoma is a rare, benign lesion of the oral cavity occurring usually in the tongue. It appears as a tumorous mass of normal bony structure with mature cells in an ectopic position. The case of a 72 years Caucasian male is presented and analyzed along with 52 similar cases reported in the English literature between 1967 and 2007. Lingual choristoma shows a female predilection, whereas the commonest anatomic location is the posterior third of the tongue, occurring at or close to the foramen caecum and the circumvallate papillae. Histologically the lesions show signs of a well-circumscribed mass of vital bone located under the surface oral epithelium. Some lesions represent developmental malformations, whereas others may be reactive lesions after trauma or chronic irritation. Treatment of lingual osseous choristoma consists of simple excision

Aerosol physical and optical properties in the Eastern Mediterranean Basin, Crete, from Aerosol Robotic Network data

In this study, we investigate the aerosol optical properties, namely aerosol extinction optical thickness (AOT), Angström parameter and size distribution over the Eastern Mediterranean Basin, using spectral measurements from the recently established FORTH (Foundation for Research and Technology-Hellas) AERONET station in Crete, for the two-year period 2003–2004. The location of the FORTH-AERONET station offers a unique opportunity to monitor aerosols from different sources. Maximum values of AOT are found primarily in spring, which together with small values of the Angström parameter indicate dust transported from African deserts, whereas the minimum values of AOT occur in winter. In autumn, large AOT values observed at near-infrared wavelengths arise also from dust transport. In summer, large AOT values at ultraviolet (340 nm) and visible wavelengths (500 nm), together with large values of the Angström parameter, are associated with transport of fine aerosols of urban/industrial and biomass burning origin. The Angström parameter values vary on a daily basis within the range 0.05–2.20, and on a monthly basis within the range 0.68–1.9. This behaviour, together with broad frequency distributions and back-trajectory analyses, indicates a great variety of aerosol types over the study region including dust, urban-industrial and biomass-burning pollution, and maritime, as well as mixed aerosol types. Large temporal variability is observed in AOT, Angström parameter, aerosol content and size. The fine and coarse aerosol modes persist throughout the year, with the coarse mode dominant except in summer. The highest values of AOT are related primarily to southeasterly winds, associated with coarse aerosols, and to a less extent to northwesterly winds associated with fine aerosols. The results of this study show that the FORTH AERONET station in Crete is well suited for studying the transport and mixing of different types of aerosols from a variety of sources, especially those associated with major dust events from the Sahara

Spatial Sound Rendering – A Survey

Simulating propagation of sound and audio rendering can improve the sense of realism and the immersion both in complex acoustic environments and dynamic virtual scenes. In studies of sound auralization, the focus has always been on room acoustics modeling, but most of the same methods are also applicable in the construction of virtual environments such as those developed to facilitate computer gaming, cognitive research, and simulated training scenarios. This paper is a review of state-of-the-art techniques that are based on acoustic principles that apply not only to real rooms but also in 3D virtual environments. The paper also highlights the need to expand the field of immersive sound in a web based browsing environment, because, despite the interest and many benefits, few developments seem to have taken place within this context. Moreover, the paper includes a list of the most effective algorithms used for modelling spatial sound propagation and reports their advantages and disadvantages. Finally, the paper emphasizes in the evaluation of these proposed works

ENSO surface shortwave radiation forcing over the tropical Pacific

International audienceWe have studied the spatial and temporal variation of the downward shortwave radiation (DSR) at the surface of the Earth during ENSO events for a 21-year period over the tropical and subtropical Pacific Ocean (40° S?40° N, 90° E?75° W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database, reanalysis data from NCEP/NCAR for the key atmospheric and surface input parameters, and aerosol parameters from GADS (acronyms explained in main text). A clear anti-correlation was found between the downward shortwave radiation anomaly (DSR-A) time-series, in the region 7° S?5° N 160° E-160° W located west of the Niño-3.4 region, and the Niño-3.4 index time-series. In this region where the highest in absolute value DSR anomalies are observed, the mean DSR anomaly values range from ?45 Wm?2 during El Niño episodes to +40 Wm?2 during La Niña events. Within the Niño-3.4 region no significant DSR anomalies are observed during the cold ENSO phase in contrast to the warm ENSO phase. A high correlation was also found over the western Pacific (10° S?5° N, 120?140° E), where the mean DSR anomaly values range from +20 Wm?2 to ?20 Wm?2 during El Niño and La Niña episodes, respectively. There is also convincing evidence that the time series of the mean downward shortwave radiation anomaly in the north subtropical Pacific region 7?15° N 150?170° E, precedes the Niño-3.4 index time-series by about 7 months. Thus, the downward shortwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to assess whether or not El Niño or La Niña conditions prevail

Ten-year global distribution of downwelling longwave radiation

International audienceDownwelling longwave fluxes, DLFs, have been derived for each month over a ten year period (1984?1993), on a global scale with a resolution of 2.5° × 2.5°. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite and reanalysis data for the key atmospheric input parameters, i.e. cloud properties, and specific humidity and temperature profiles. The cloud climatologies were taken from the latest released and improved International Satellite Climatology Project D2 series. Specific humidity and temperature vertical profiles were taken from three different reanalysis datasets; NCEP/NCAR, GEOS, and ECMWF (acronyms explained in main text). DLFs were computed for each reanalysis dataset, with differences reaching values as high as 30 Wm?2 in specific regions, particularly over high altitude areas and deserts. However, globally, the agreement is good, with the rms of the difference between the DLFs derived from the different reanalysis datasets ranging from 5 to 7 Wm?2. The results are presented as geographical distributions and as time series of hemispheric and global averages. The DLF time series based on the different reanalysis datasets show similar seasonal and inter-annual variations, and similar anomalies related to the 86/87 El Niño and 89/90 La Niña events. The global ten-year average of the DLF was found to be between 342.2 Wm?2 and 344.3 Wm?2, depending on the dataset. We also conducted a detailed sensitivity analysis of the calculated DLFs to the key input data. Plots are given that can be used to obtain a quick assessment of the sensitivity of the DLF to each of the three key climatic quantities, for specific climatic conditions corresponding to different regions of the globe. Our model downwelling fluxes are validated against available data from ground-based stations distributed over the globe, as given by the Baseline Surface Radiation Network. There is a negative bias of the model fluxes when compared against BSRN fluxes, ranging from ?7 to ?9 Wm?2, mostly caused by low cloud amount differences between the station and satellite measurements, particularly in cold climates. Finally, we compare our model results with those of other deterministic models and general circulation models

Global distribution of Earth's surface shortwave radiation budget

International audienceThe monthly mean shortwave (SW) radiation budget at the Earth's surface (SRB) was computed on 2.5-degree longitude-latitude resolution for the 17-year period from 1984 to 2000, using a radiative transfer model accounting for the key physical parameters that determine the surface SRB, and long-term climatological data from the International Satellite Cloud Climatology Project (ISCCP-D2). The model input data were supplemented by data from the National Centers for Environmental Prediction - National Center for Atmospheric Research (NCEP-NCAR) and European Center for Medium Range Weather Forecasts (ECMWF) Global Reanalysis projects, and other global data bases such as TIROS Operational Vertical Sounder (TOVS) and Global Aerosol Data Set (GADS). The model surface radiative fluxes were validated against surface measurements from 22 stations of the Baseline Surface Radiation Network (BSRN) covering the years 1992-2000, and from 700 stations of the Global Energy Balance Archive (GEBA), covering the period 1984-2000. The model is in good agreement with BSRN and GEBA, with a negative bias of 14 and 6.5 Wm-2, respectively. The model is able to reproduce interesting features of the seasonal and geographical variation of the surface SW fluxes at global scale. Based on the 17-year average model results, the global mean SW downward surface radiation (DSR) is equal to 171.6 Wm-2, whereas the net downward (or absorbed) surface SW radiation is equal to 149.4 Wm-2, values that correspond to 50.2 and 43.7% of the incoming SW radiation at the top of the Earth's atmosphere. These values involve a long-term surface albedo equal to 12.9%. Significant increasing trends in DSR and net DSR fluxes were found, equal to 4.1 and 3.7 Wm-2, respectively, over the 1984-2000 period (equivalent to 2.4 and 2.2 Wm-2 per decade), indicating an increasing surface solar radiative heating. This surface SW radiative heating is primarily attributed to clouds, especially low-level, and secondarily to other parameters such as total precipitable water. The surface solar heating occurs mainly in the period starting from the early 1990s, in contrast to decreasing trend in DSR through the late 1980s. The computed global mean DSR and net DSR flux anomalies were found to range within ±8 and ±6 Wm-2, respectively, with signals from El Niño and La Niña events, and the Pinatubo eruption, whereas significant positive anomalies have occurred in the period 1992-2000

Analysis of the decrease in the tropical mean outgoing shortwave radiation at the top of atmosphere for the period 1984-2000

International audienceA decadal-scale trend in the tropical radiative energy budget has been observed recently by satellites, which however is not reproduced by climate models. In the present study, we have computed the outgoing shortwave radiation (OSR) at the top of atmosphere (TOA) at 2.5° longitude-latitude resolution and on a mean monthly basis for the 17-year period 1984-2000, by using a deterministic solar radiative transfer model and cloud climatological data from the International Satellite Cloud Climatology Project (ISCCP) D2 database. Anomaly time series for the mean monthly pixel-level OSR fluxes, as well as for the key physical parameters, were constructed. A significant decreasing trend in OSR anomalies, starting mainly from the late 1980s, was found in tropical and subtropical regions (30° S-30° N), indicating a decadal increase in solar planetary heating equal to 1.9±0.3Wm-2/decade, reproducing well the features recorded by satellite observations, in contrast to climate model results. This increase in solar planetary heating, however, is accompanied by a similar increase in planetary cooling, due to increased outgoing longwave radiation, so that there is no change in net radiation. The model computed OSR trend is in good agreement with the corresponding linear decadal decrease of 2.5±0.4Wm-2/decade in tropical mean OSR anomalies derived from ERBE S-10N non-scanner data (edition 2). An attempt was made to identify the physical processes responsible for the decreasing trend in tropical mean OSR. A detailed correlation analysis using pixel-level anomalies of model computed OSR flux and ISCCP cloud cover over the entire tropical and subtropical region (30° S-30° N), gave a correlation coefficient of 0.79, indicating that decreasing cloud cover is the main reason for the tropical OSR trend. According to the ISCCP-D2 data derived from the combined visible/infrared (VIS/IR) analysis, the tropical cloud cover has decreased by 6.6±0.2% per decade, in relative terms. A detailed analysis of the inter-annual and long-term variability of the various parameters determining the OSR at TOA, has shown that the most important contribution to the observed OSR trend comes from a decrease in low-level cloud cover over the period 1984-2000, followed by decreases in middle and high-level cloud cover. Note, however, that there still remain some uncertainties associated with the existence and magnitude of trends in ISCCP-D2 cloud amounts. Opposite but small trends are introduced by increases in cloud scattering optical depth of low and middle clouds