Foregrounds for redshifted 21 cm studies of reionization: GMRT 153 MHz observations

Foreground subtraction is the biggest challenge for future redshifted 21 cm observations to probe reionization. We use a short GMRT observation at 153 MHz to characterize the statistical properties of the background radiation across ~ one degree to sub-arcminutes angular scales, and across a frequency band of 5 MHz with 62.5 kHz resolution. The statistic we use is the visibility correlation function, or equivalently the angular power spectrum C_l. We present the results obtained from using relatively unsophisticated, conventional data calibration procedures. We find that even fairly simple minded calibration allows one to estimate the visibility correlation function at a given frequency V_2(U,0). From our observations we find that V_2(U,0) is consistent with foreground model predictions at all angular scales except the largest ones probed by our observations where the the model predictions are somewhat in excess. On the other hand the visibility correlation between different frequencies kappa(U, Delta nu), seems to be much more sensitive to calibration errors. We find a rapid decline in kappa(U, Delta nu), in contrast with the prediction of less than 1 % variation across 2.5 MHz. In this case however, it seems likely that a substantial part of the discrepancy may be due to limitations of data reduction procedures.Comment: 10 pages, 7 figures, 1 table, Accepted for Publication in MNRA

Stock assessment of bonyfishes in the Iranian coastal water of the Caspian Sea (2004-2005)

For gathering of data on biometry and catch statistics, 5 mobile working group in the regions of Anzali, Kiashahr , Noshahr , Babolsar and Torkmen were involved from the start (2004.10.23) to the end of fishing season (2005.04.10). Gathered data were entered to the computer based on species. For data analysis different methods were undertaken such as Bertallanfy equation for growth parameter Beverton and Holt for total mortality rates, pauly's imperical model for natural mortality rate and cohort Analysis for biomass estimation. Total catch with taking into account of poaching, was estimated 15140 tons reported by scientific committee of catch and fishing harbor relief of Iranian Fishery Company. The total recorded catch of beach seine cooperatives was 10644 tons that comprise 70.2% of the total catch. Total catch of Caspian Kutum was estimated 6612 tons that had 1856 tons (22%) decrease with comparison of the last year. Biomass of Caspian kutum in Iranian coastal Water of the Caspian Sea in 2003-2004 estimated about 20400 tons. The total catch of golden gray mullet was estimated 4425.6 tons that constitute 29.2% of total catch of bony fishes. Biomass of this species was estimated 12200 tons and based on this amount of biomass, Maximum Sustainable Yield (MSY) was calculated as 3577 tons. Long nose mullet comprised only 1.4% of the mullet catch. The catch of common carp in 2004-2005 fishing season continued its increasing trend and caught in amount of 3087 tons by beach seine cooperatives that had 2.2 fold increase in comparison of previous fishing season. Most of the catch occurred in Golestan province and was immature and undersize and the length frequency modes showed moving towards bigger size and older age groups in comparison of previous fishing season. The catch of pick perch in 2003-2004 decreased with comparison of the last year and estimated about 22.5 tons. Most of the catch of pick perch was immature and undersize. Approximately all of the catch is due to releasing of fingerling of this species by Fishery Company especially in Guilan province. Total catch of bream was estimated 27.4 tons and most of which was immature and undersize. Population of asp is critically endangered and the catch of this species is very low (500 kg). Restocking of this species must be considered by Iranian fishing company

The study and feasibility of Cheshmeh-Ali River and down stream area of Shahid Shah-Charaghy Dam in Damghan for aquaculture development

This research was conducted to finding of Cheshmeh-Ali and Shahcheraghi-Dam downstream areas potential for developing of aquaculture industry. The present study was conducted based on available information and data from monthly and seasonally sampling including geographical area, margin lands and fluctuations of river water, seasonal climatic changes view point of rainfall, temperature, wet, evaporation, wind velocity, sunshine hours, frost and also chemical and physical parameters of water including temperature, alkalinity, total hardness, chloride, calcium, magnesium, sodium, potassium, organic phosphorous and nitrogen, suspended solids, turbidity, water flow and flood conditions, and in addition phytoplankton and zooplankton communities, macrobenthic invertebrates, fishes, aquatic plants, amphibians, reptiles, birds. Results showed that the upstream and downstream regions of Shahcheraghi dam are not suitable for warm water aquaculture in earthen ponds. But view point of cold-water aquaculture, particularly trout, there are some good situations. Also it can be suggested different culture systems including of race way, octagonal concrete ponds, semi-circulation and circulation methods. But, due to water restrictions in the area, semi-circulation and circulation system is preferred. In ideal conditions can be produced about 1,600 tones of trout, if all the capacity of this area be used for aquaculture. Otherwise, in limited circumstances view point of exploitation possibility of the water, only about 700 tons can be produced. In addition, there were appropriate facilities in spring area of Cheshmehali for tourism industry, that it can be considered as priorities for economic development in the region. Due to the low sensitivity of the ecologically conditions, native or exotic aquatic species rearing in indoor methods can be recommended

Cosmology at Low Frequencies: The 21 cm Transition and the High-Redshift Universe

Observations of the high-redshift Universe with the 21 cm hyperfine line of neutral hydrogen promise to open an entirely new window onto the early phases of cosmic structure formation. Here we review the physics of the 21 cm transition, focusing on processes relevant at high redshifts, and describe the insights to be gained from such observations. These include measuring the matter power spectrum at z~50, observing the formation of the cosmic web and the first luminous sources, and mapping the reionization of the intergalactic medium. The epoch of reionization is of particular interest, because large HII regions will seed substantial fluctuations in the 21 cm background. We also discuss the experimental challenges involved in detecting this signal, with an emphasis on the Galactic and extragalactic foregrounds. These increase rapidly toward low frequencies and are especially severe for the highest redshift applications. Assuming that these difficulties can be overcome, the redshifted 21 cm line will offer unique insight into the high-redshift Universe, complementing other probes but providing the only direct, three-dimensional view of structure formation from z~200 to z~6.Comment: extended review accepted by Physics Reports, 207 pages, 44 figures (some low resolution); version with high resolution figures available at http://pantheon.yale.edu/~srf28/21cm/index.htm; minor changes to match published versio

Sickle Cell Trait and Kidney Disease in People of African Ancestry With HIV

Introduction: Sickle cell trait (SCT) has been associated with chronic kidney disease (CKD) in African Americans, although evidence for its impact in Africans and people with HIV is currently lacking. We conducted a cross-sectional study investigating the association between SCT and kidney disease in people of African ancestry with HIV in the UK. Methods: The primary outcome was estimated glomerular filtration rate (eGFR) 50 mg/mmol), and albuminuria (albumin-to-creatinine ratio >3 mg/mmol). Multivariable logistic regression was used to estimate the associations between SCT and kidney disease outcomes. Results: A total of 2895 participants (mean age 48.1 [SD 10.3], 57.2% female) were included, of whom 335 (11.6%) had SCT and 352 (12.2%) had eGFR <60 ml/min per 1.73 m2. After adjusting for demographic, HIV, and kidney risk factors including APOL1 high-risk genotype status, individuals with SCT were more likely to have eGFR <60 ml/min per 1.73 m2 (odds ratio 1.62 [95% CI 1.14–2.32]), eGFR <90 ml/min per 1.73 m2 (1.50 [1.14–1.97]), and albuminuria (1.50 [1.09–2.05]). Stratified by APOL1 status, significant associations between SCT and GFR <60 ml/min per 1.73 m2, eGFR <90 ml/min per 1.73 m2, proteinuria, and albuminuria were observed for those with APOL1 low-risk genotypes. Conclusion: Our results extend previously reported associations between SCT and kidney disease to people with HIV. In people of African ancestry with HIV, these associations were largely restricted to those with APOL1 low-risk genotypes

Genetic Variants of APOL1 Are Major Determinants of Kidney Failure in People of African Ancestry With HIV

INTRODUCTION: Variants of the APOL1 gene are associated with chronic kidney disease (CKD) in people of African ancestry, although evidence for their impact in people with HIV are sparse. METHODS: We conducted a cross-sectional study investigating the association between APOL1 renal risk alleles and kidney disease in people of African ancestry with HIV in the UK. The primary outcome was end-stage kidney disease (ESKD; estimated glomerular filtration rate [eGFR] of 30 mg/mmol), and biopsy-proven HIV-associated nephropathy (HIVAN). Multivariable logistic regression was used to estimate the associations between APOL1 high-risk genotypes (G1/G1, G1/G2, G2/G2) and kidney disease outcomes. RESULTS: A total of 2864 participants (mean age 48.1 [SD 10.3], 57.3% female) were genotyped, of whom, 354 (12.4%) had APOL1 high-risk genotypes, and 99 (3.5%) had ESKD. After adjusting for demographic, HIV, and renal risk factors, individuals with APOL1 high-risk genotypes were at increased odds of ESKD (odds ratio [OR] 10.58, 95% CI 6.22–17.99), renal impairment (OR 5.50, 95% CI 3.81–7.95), albuminuria (OR 3.34, 95% CI 2.00–5.56), and HIVAN (OR 30.16, 95% CI 12.48–72.88). An estimated 49% of ESKD was attributable to APOL1 high-risk genotypes. CONCLUSION: APOL1 high-risk genotypes were strongly associated with kidney disease in people of African ancestry with HIV and accounted for approximately half of ESKD cases in this cohort