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Recent studies have challenged the validity of the Redfield ratio. It is proposed that physical and biogeochemical processes govern the geographical variations in carbon : nitrogen : phosphorus (C : N : P) ratios. However, this proposal remains to be examined through concurrent observations of C : N : P ratios with physical and biogeochemical processes in various marine reservoirs. Here, we sampled the Arabian Sea for its C, N, and P content in organic and inorganic pools during the winter monsoon. We analyzed the role of convective mixing, eddies, and N2 fixation to explain the variation in observed elemental ratios. Convective mixing injected the cold water and enhanced the supply of N and P nutrients in the top layer (surface to 50–75 m) of the northern Arabian Sea. This led to a decrease in the N : P and C : P ratios in the particulate organic matter in the northern region, but C : N : P increased equatorward, averaging 245 : 32 : 1 in the top layer of the Arabian Sea. The variation in the elemental ratios in the top layer is best explained by the changes in water temperature. N2 fixation contributed negligibly to the N : P ratio of the export flux. The substantial decrease in N : P ratios of nutrients in the subsurface waters is most likely caused by the denitrifying conditions in the Arabian Sea. As the processes of convective mixing and eddies are are prevalent oceanic processes, our observations underpin that the interplay of these processes leads to changes in the elemental ratios globally. [ABSTRACT FROM AUTHOR]

Black carbon (BC) has emerged as an integral part of the global carbon (C) cycle, constituting 12% ± 5% of the organic C pool in rivers and soils, with the potential to generate negative climate feedback. However, its ability to sequester C depends on the recalcitrant nature of BC in the environment, which is under debate. Using CTO‐375 method and by measuring concentrations and isotopic compositions of particulate BC (δ13CPBC), we explore the transformation of particulate black carbon (PBC) along the atmosphere‐river‐ocean continuum. Significantly high δ13CPBC in the ocean compared to rivers and atmospheric particulate matter indicates (a) degradation of PBC, potentially through photodegradation and leaching, and/or (b) availability of an enriched source other than fluvial or aeolian inputs. This evidence for degradation of PBC in aquatic systems warrants rethinking on its C sequestration potential and role in aquatic C biogeochemistry and further raises concerns regarding the use of sedimentary BC as a paleoenvironmental proxy. Plain Language Summary: Particulate black carbon (PBC) forms ∼12% ± 5% of the particulate organic carbon pool in aquatic systems. Black carbon has been considered highly recalcitrant and therefore a potent sink for carbon. Paleo‐environmental and biogeochemical studies have been conducted assuming BC as highly stable and its isotopic composition to remain unaltered after formation. This study explores the variability in stable isotopic composition of PBC in the riverine, atmospheric, and oceanic systems and provides evidence contrary to the general belief of the refractory nature of BC, which warrants revisiting and rethinking of the BC dynamics in aquatic systems. Key Points: Particulate black carbon (PBC) concentration decreases along the river ocean continuumStable carbon isotopic composition of the oceanic PBC pool is higher compared to the riverine and atmospheric poolsIsotopic evidence suggests degradation of PBC with the preferential loss of lighter carbon [ABSTRACT FROM AUTHOR]

Objective: To determine the frequency of common bacteria and their antibiotic sensitivity in patients with symptomatic cholelithiasis Methodology: This cross sectional descriptive study was conducted at Department of Surgery, Lady reading hospital, Peshawar for 6 months i.e., from December 2012 to May 2013. The total number of patients were 126. They presented with symptomatic cholelithiasis. Bile was aspirated peroperatively before cholecystectomy from gall bladder and was sent for culture and sensitivity test. The data was analyzed using Statistical Package for Social Sciences (SPSS) version 10.0. Results: On culture and sensitivity test, 74 (58.73%) have positive growth while 52 (41.27%) have no growth. The most common bacteria was E. Coli isolated in 28 (22.22%) patients followed by Klebseilla in 22 (17.46%), Salmonella in 16 (12.70%) and Shigella in 8 (6.35%) patients. On culture and sensitivity test, all the 4 isolated bacteria showed sensitivity to Cefuroxime, Ceftriaxone and Ciprofloxacin in more than 50 % cases, while all the four bacteria showed resistance to amoxicillin in more than 50 % cases. Conclusion: The most common bacteria of symptomatic cholelithiasis are E. coli and Klebseilla followed by Salmonella and Shigella. These bacteria showed maximum sensitive to cefuroxime and ceftriaxone. [ABSTRACT FROM AUTHOR]