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Tehrān, Iran

Zolfonoun E.,Nuclear Science and Technology Research Institute, Iran | Salahinejad M.,Environmental Laboratory
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

A new simple and rapid vortex-assisted liquid-liquid microextraction method was applied for the determination of thorium in water samples. In this method, chloroform used as extraction solvent was directly injected into the water sample solution. The extraction solvent was dispersed into the aqueous phase under vigorously shaking with the vortex. After centrifuging, the fine droplets of extractant phase were settled to the bottom of the conical-bottom centrifuge tube. The effect of different experimental parameters on the performance of the method were studied and discussed. Under the optimum conditions, the detection limit for Th(IV) was 7.5 ng mL-1. The precision of the method, evaluated as the relative standard deviation obtained by analyzing of 10 replicates, was 2.8 %. The practical applicability of the developed method was examined using natural water and monazite sand samples. © 2013 Akadémiai Kiadó, Budapest, Hungary. Source


News Article
Site: https://www.sciencenews.org/

A rapid loss of phytoplankton threatens to turn the western Indian Ocean into an “ecological desert,” a new study warns. The research reveals that phytoplankton populations in the region fell an alarming 30 percent over the last 16 years. A decline in ocean mixing due to warming surface waters is to blame for that phytoplankton plummet, researchers propose online January 19 in Geophysical Research Letters. The mixing of the ocean’s layers ferries phytoplankton nutrients from the ocean’s dark depths up into the sunlit layers that the mini plants inhabit. The loss of these microbes, which form the foundation of the ocean food web, may undermine the region’s ecosystem, warns study coauthor Raghu Murtugudde, an oceanographer at the University of Maryland in College Park. “If you reduce the bottom of the food chain, it’s going to cascade,” Murtugudde says. The phytoplankton decline may be partially responsible for a 50 to 90 percent decline in tuna catch rates over the last half-century in the Indian Ocean, he says. “This is a wake-up call to look if similar things are happening elsewhere.” In the 20th century, surface temperatures in the Indian Ocean rose about 50 percent more than the global average. Previous investigations into this ocean warming’s impact on phytoplankton suggested that populations had increased. But those studies looked at only a few years of data — not long enough to clearly identify any long-term trend. Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology in Pune, Murtugudde and colleagues tracked the microscopic phytoplankton from space. Phytoplankton, like land plants, are tinted green. When the sea surface is filled with phytoplankton, the water takes on a lighter, greener tinge. As the phytoplankton population thins, the water turns darker and bluer. Analyzing satellite images of ocean color collected over the last 16 years, the researchers found a 30 percent drop in the abundance of green-tinted microbes per cubic meter of water. Combining this data with computer simulations of the Indian Ocean, the researchers reconstructed the ups and downs of phytoplankton in the region over the last six decades. That work suggests that phytoplankton populations in the western Indian Ocean have declined 20 percent relative to 1950. Warming surface temperatures resulted in the long-term drop in phytoplankton, the ocean simulations revealed. To survive, phytoplankton rely on nitrates produced by bacteria that dwell around 100 to 500 meters below the sea surface. Those nitrates are churned upward by such forces as winds blowing over the ocean surface. Warmer water is less dense and stays near the surface. As the sea surface becomes warmer relative to the deeper ocean due to climate change, the two layers become harder to mix and nutrients become scarcer in the sunlit top layer. Upcoming ship-based studies should verify the new results, says Michael McPhaden, a physical oceanographer at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle. Piracy off the coast of Somalia had up until recently prevented research vessels from studying parts of the western Indian Ocean, but this year marks the beginning of a five-year Indian Ocean expedition. “This work includes logical leaps that are sensible to make based on what we know about how the system works, but you always want to go out and verify,” McPhaden says.


Edwards C.E.,Environmental Laboratory | Parchman T.L.,University of Wyoming | Weekley C.W.,Archbold Biological Station
DNA Research | Year: 2012

Large-scale DNA sequence data may enable development of genetic resources in endangered species, thereby facilitating conservation efforts. Ziziphus celata, a federally endangered, self-incompatible plant species occurring in Florida, USA, is one species for which genetic resources are necessary to facilitate new introductions and augmentations essential for recovery of the species. We used 454 pyrosequencing of a Z. celata normalized floral cDNA library to create a genomic resource for gene and marker discovery. A half-plate GS-FLX Titanium run yielded 655 337 reads averaging 250 bp. A total of 474 025 reads were assembled de novo into 84 645 contigs averaging 408 bp, while 181 312 reads remained unassembled. Forty-seven and 43% of contig consensus sequences had BLAST matches to known proteins in the Uniref50 and TAIR9 annotated protein databases, respectively; many contigs fully represented orthologous proteins in TAIR9. A total of 22 707 unique genes were sequenced, indicating substantial coverage of the Z. celata transcriptome. We detected single-nucleotide polymorphisms and simple sequence repeats (SSRs) and developed thousands of SSR primers for use in future genetic studies. As a first step towards understanding self-incompatibility in Z. celata, we identified sequences belonging to the gene family encoding self-incompatibility. This study demonstrates the efficacy of 454 transcriptome sequencing for rapid gene and marker discovery in an endangered plant. © 2011 The Author. Source


Salahinejad M.,Environmental Laboratory | Ghasemi J.B.,K. N. Toosi University of Technology
Ecotoxicology and Environmental Safety | Year: 2014

Three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis were performed on the toxicity of a large set of substituted benzenes toward ciliate Tetrahymena pyriformis. The 3D-QSAR studies were carried out using comparative molecular fi{ligature}eld analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA) and VolSurf techniques.The optimal CoMFA and CoMSIA models obtained from the training set were all statistically significant with correlation coefficients (R2) greater than 0.79 and absolute error less than 0.33 in log units. The predictive ability of the models was externally evaluated through the prediction of a test set (20 percent of the whole data set) that were not included in the training set. A simple and fairly good predictive linear model based on VolSurf descriptors was also developed that showed an adequate prediction power of the toxicity (pIGC50) of substituted benzenes. Validation, reliability and robustness of models were also evaluated by leave-one-out, leave-four-out, bootstrapping and progressive scrambling approaches.The results confirmed that in addition to hydrophobic effects, electrostatic and H-bonding interactions also play important roles in the toxicity of substituted benzenes. The information obtained from CoMFA and CoMSIA 3-D contour maps could be useful to explain the toxicity mechanism of substituted benzenes. © 2013 Elsevier Inc. Source


Salahinejad M.,Environmental Laboratory
Journal of Radioanalytical and Nuclear Chemistry | Year: 2015

Three (3D) and two dimensional (2D) quantitative structure–property relationships (QSPR) were established to model of the complexation formation of bifunctional coupling agents with 64Cu(II) and 67/68Ga(III) radiometal ions. The best model for 3D-QSPR has been obtained with R2 > 0.93 and Q2 > 0.75. Some simple 2D-QSAR models, able to correlate and predict the formation constants are developed. The final models satisfied a set of rigorous validation criteria and performed well in the prediction of an external test set. The information obtained could be very useful to design the most efficient ligands and find new matching chelators to radiometals for radiopharmaceuticals applications. © 2014, Akadémiai Kiadó, Budapest, Hungary. Source

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