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

Response to Defoliation of Tall Fescue

An experiment studying the behaviour of toll fescue (Fesutca anrundinacea Schreb,) was conducted under steady stale grazing on a sward dominated by this plant. The swards were grazed lo maintain a surface height of 30-40 mm (H), 50-60 mm (M) and 90-100 mm (L). These treatments were applied on swards with and without white clover (Trifolium repens L.) from November 1990 to April 1991. Results showed that leaf growth decreased as the severity of grazing increased. Tiller number was less under H grazing than under M or L grazing, but tiller size remained constant over time in this treatment. Herbage mass was greater under M and L grazing than that under H grazing as a consequence of differences in total tiller population density and tiller size. Invasion of tall fescue swards by other grasses, especially perennial ryegrass (lolium perenne L.) was greater than that by while clover

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

Optimal Rate for Irregular LDPC Codes in Binary Erasure Channel

In this paper, we introduce a new practical and general method for solving the main problem of designing the capacity approaching, optimal rate, irregular low-density parity-check (LDPC) code ensemble over binary erasure channel (BEC). Compared to some new researches, which are based on application of asymptotic analysis tools out of optimization process, the proposed method is much simpler, faster, accurate and practical. Because of not using any relaxation or any approximate solution like previous works, the found answer with this method is optimal. We can construct optimal variable node degree distribution for any given binary erasure rate, {\epsilon}, and any check node degree distribution. The presented method is implemented and works well in practice. The time complexity of this method is of polynomial order. As a result, we obtain some degree distribution which their rates are close to the capacity.Comment: 5 pages, to be presented at the 2011 IEEE Information Theory Workshop (ITW 2011), Paraty, Brazil, October, 201

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