Loop quantum effect and the fate of tachyon field collapse

We study the fate of gravitational collapse of a tachyon field matter. In presence of an inverse square potential a black hole forms. Loop quantum corrections lead to the avoidance of classical singularities, which is followed by an outward flux of energy.Comment: Contribution to the conference of Loops'11, Madri

An investigation on the sturgeon stocks in southern Caspian Sea

We launched a summer and winter cruise using two fishing vessels to assess the stocks of the sturgeon fish in the southern coasts of the Caspian Sea in the year 2004-2005. Eighty five random stations were selected and sampled using a 9 meter trawl in waters less than 10 meters and a 24.7 meter trawl for the depths above 10 meters. We caught 170 sturgeons in the summer cruise which comprised 142 Acipenser persicus, 19 Acipenser stellatus, 4 Huso huso, 3 Acipenser nudiventris and 2 Acipenser guldenstadtti. In the winter cruise, 118 sturgeons were caught of which 75 were A. persicus, 41 were A. stellatus, 1 was A. nudiventris and 1 was A. guldenstadtti. Catch per unit effort (CPUE) was calculated as 2 fish for summer cruise with the A. persicus being the most abundant species with 1.67 individuals per trawling while for A. stellatus this was 0.22. For H. huso, the CPUE was 0.05 and for A. nudiventris it was 0.04. For winter cruise, the CPUE was calculated as 1.38 fish, again with the A. persicus as the most abundant with 0.88, while that of the A. stellatus was 0.48. The CPUE for A. guldenstadtti and A. nudiventris was 0.01 in the winter cruise

Evaluation of different sensing approaches concerning to nondestructive estimation of leaf area index (LAI) for winter wheat

Different approaches of non-destructive estimation of the LAI in winter wheat were compared. Plant height had weak relation with the LAI, while estimated biomass showed high logarithmic relationship (R2=0.839). NDRE and REIP were logarithmically well related to the LAI (R2=0.726 and 0.779 respectively). Saturation effect of NDRE and REIP was less than NDVI. Some RGB-based indices also showed good potential to estimate the LAI. Among the indices, Gm, GMB, RMB, and NRMB were better related to the LAI. The results indicated that digital cameras can be used as an affordable and simple approach for assessment of the LAI of crops

Stock assessment of juvenile sturgeons in the Iranian water of the Caspian Sea by bottom trawl survey

The sturgeon stock assessment was performed to aim at estimation of absolute and relative abundance and determination of species composition at lower 10 m depths using the Si-Sara2 RV vessel in the Iranian coasts of the Caspian Sea in Guilan, Mazandaran and Golestan provinces during 6-30 September 2011-2012. In this study, 40 stations were selected on the basis of stratified random sampling design and then the stock estimation was performed using the swept area method. The study was carried out using bottom trawling with 9 m head rope. The time and speed of trawling in each station were 30 minutes and 2.5 knots respectively. The Catch per Unit of Effort (CPUE) in 2011–2012 were 7.03 and 6.96 individuals per trawling, respectively. The catch per unit of area in these years were found to be 1662 and 1644 fish in nm2, respectively.Total abundance of sturgeon juveniles was 13,327,164 individuals in 2011. So, the species composition included A. persicus (87.8%) and A. stellatus (12.2%). Total abundance of sturgeon juveniles was found to be 14,364,882 individuals in 2012 and the species composition comprised A. persicus (61.4%) and A. stellatus (38.6%). In 2011 the biomass of sturgeons in Iranian coastal water of the Caspian Sea was 295 tons and the composition of biomass included A. persicus (81.5%) and A. stellatus (18.5%), respectively. In the cruises conducted in 2011, this amount was estimated to be 217 tons comprising A. persicus (54.2%) and A. stellatus (45.8%), respectively. The results of this study in 2011–2012 showed remarkable abundance of juvenile sturgeons in Iranian coastal waters of the Caspian Sea in late summer and early autumn. So, by conserving these valuable stocks, the number of spawners will be increased in the future

Investigation of correlation of the variations in land subsidence (detected by continuous GPS measurements) and methodological data in the surrounding areas of Lake Urmia

Lake Urmia, a salt lake in the north-west of Iran, plays a valuable role in the environment, wildlife and economy of Iran and the region, but now faces great challenges for survival. The Lake is in immediate and great danger and is rapidly going to become barren desert. As a result, the increasing demands upon groundwater resources due to expanding metropolitan and agricultural areas are a serious challenge in the surrounding regions of Lake Urmia. The continuous GPS measurements around the lake illustrate significant subsidence rate between 2005 and 2009. The objective of this study was to detect and specify the non-linear correlation of land subsidence and temperature activities in the region from 2005 to 2009. For this purpose, the cross wavelet transform (XWT) was carried out between the two types of time series, namely vertical components of GPS measurements and daily temperature time series. The significant common patterns are illustrated in the high period bands from 180–218 days band (~6–7 months) from September 2007 to February 2009. Consequently, the satellite altimetry data confirmed that the maximum rate of linear trend of water variation in the lake from 2005 to 2009, is associated with time interval from September 2007 to February 2009. This event was detected by XWT as a critical interval to be holding the strong correlation between the land subsidence phenomena and surface temperature. Eventually the analysis can be used for modeling and prediction purposes and probably stave off the damage from subsidence phenomena