Aim. To determine the antimicrobial potential of guava (Psidium guajava) leaf extracts against two gram-negative bacteria (Escherichia coli and Salmonella enteritidis) and two gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) which are some of foodborne and spoilage bacteria. The guava leaves were extracted in four different solvents of increasing polarities (hexane, methanol, ethanol, and water). The efficacy of these extracts was tested against those bacteria through a well-diffusion method employing 50 μL leaf-extract solution per well. According to the findings of the antibacterial assay, the methanol and ethanol extracts of the guava leaves showed inhibitory activity against gram-positive bacteria, whereas the gram-negative bacteria were resistant to all the solvent extracts. The methanol extract had an antibacterial activity with mean zones of inhibition of 8.27 and 12.3 mm, and the ethanol extract had a mean zone of inhibition of 6.11 and 11.0 mm against B. cereus and S. aureus, respectively. On the basis of the present finding, guava leaf-extract might be a good candidate in the search for a natural antimicrobial agent. This study provides scientific understanding to further determine the antimicrobial values and investigate other pharmacological properties.

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The Himalayan-sourced Ganges-Brahmaputra river system and the deep-sea Bengal Fan represent Earth’s largest sediment-dispersal system. Here we present detrital zircon U-Pb provenance data from Miocene to middle Pleistocene Bengal Fan turbidites, and evaluate the influence of allogenic forcing vs. autogenic processes on signal propagation from the Himalaya to the deep sea. Our data record the strong tectonic and climatic forcing characteristic of the Himalayan system: after up to 2500 km of river transport, and >1400 km of transport by turbidity currents, the U-Pb record faithfully represents Himalayan sources. Moreover, specific U-Pb populations record Miocene integration of the Brahmaputra drainage with the Asian plate, as well as the rapid Plio-Pleistocene incision through, and exhumation of, the eastern Himalayan syntaxis. The record is, however, biased towards glacial periods when rivers were extended across the shelf in response to climate-forced sea-level fall, and discharged directly to slope canyons. Finally, only part of the record represents a Ganges or Brahmaputra provenance end-member, and most samples represent mixing from the two systems. Mixing or the lack thereof likely represents the fingerprint of autogenic delta-plain avulsions, which result in the two rivers delivering sediment separately to a shelf-margin canyon or merging together as they do today.

Higgins, SA, et al. 2018 River linking in India: Downstream impacts on water discharge and suspended sediment transport to deltas. Elem Sci Anth, 6: 20. DOI: https://doi.org/10.1525/elementa.269 IntroductionTo expand agricultural production and address water scarcity, India is moving forward with a large-scale civil engineering project to connect 44 rivers via a vast network of canals (Joshi, 2013;Bagla, 2014). The National River Linking Project, or NRLP, aims to increase irrigated area by 350,000 km 2 and improve food security and clean water access. India receives between 50 and 90% of its annual precipitation during the summer monsoon, during which time water is abundant and floods are common. The NRLP will store and redistribute this water in an effort to reduce temporal and spatial inconsistencies in supply. The project is intended to address the substantial challenges of food production and clean water access that India will face in the coming century -challenges that are being confronted globally as countries face rising temperatures, and increasing populations with stressed water supplies ( Wallace, 2000;Battisti and Naylor, 2009;Hanjra and Qureshi, 2010). Interbasin water transfer systems are a common solution to water scarcity, and the NRLP is the largest of many new diversion schemes proposed or underway in China, Brazil, and Central Africa (Zhang, 2009; Lemoalle et al., 2012). However, large-scale river diversion projects such as the NRLP can result in farreaching consequences for downstream river discharge and delta maintenance. For example, due to damming, diversions, and increased water usage, the Colorado, Nile, Indus and Yellow (Huanghe) rivers discharge little to no sediment today, whereas they previously accounted for 10% of the global sediment flux to the ocean (Syvitski and Milliman, 2007).The NRLP in its current form was designed in the early 1980s, when the Indian government established the National Water Development Agency (NWDA) to manage implementation of the project. The project stalled between the 1980s and the 2010s, but it was renewed in RESEARCH ARTICLERiver linking in India: Downstream impacts on water discharge and suspended sediment transport to deltas To expand agricultural production and address water scarcity, India is moving forward with the National River Linking Project (NRLP), which will connect 44 rivers via 9,600 km of canals. Here, we compile the first complete database of proposed NRLP dams, reservoirs and canals, including operating schedules for Himalayan infrastructure. We evaluate potential NRLP-derived changes to mean annual water discharge for 29 rivers and mean monthly water and sediment discharge for six rivers flowing to five major deltas. Sediment rating curves are used to quantify the impacts of changing water discharge within the rivers, and basin-wide trapping efficiency is established for new reservoirs. Given full implementation of the NRLP, we forecast reductions in annual suspended sediment transport to deltas of 40-85% (Mahanadi), 71-99% (Godavari) ...