Urinary levels of N-nitroso compounds in relation to risk of gastric cancer: Findings from the Shanghai cohort study

Background: N-Nitroso compounds are thought to play a significant role in the development of gastric cancer. Epidemiological data, however, are sparse in examining the associations between biomarkers of exposure to N-nitroso compounds and the risk of gastric cancer. Methods: A nested case-control study within a prospective cohort of 18,244 middle-aged and older men in Shanghai, China, was conducted to examine the association between urinary level of N-nitroso compounds and risk of gastric cancer. Information on demographics, usual dietary intake, and use of alcohol and tobacco was collected through in-person interviews at enrollment. Urinary levels of nitrate, nitrite, N-nitroso-2-methylthiazolidine-4-carboxylic acid (NMTCA), N-nitrosoproline (NPRO), N-nitrososarcosine (NSAR), N-nitrosothiazolidine-4-carboxylic acid (NTCA), as well as serum H. pylori antibodies were quantified in 191 gastric cancer cases and 569 individually matched controls. Logistic regression method was used to assess the association between urinary levels of N-nitroso compounds and risk of gastric cancer. Results: Compared with controls, gastric cancer patients had overall comparable levels of urinary nitrate, nitrite, and N-nitroso compounds. Among individuals seronegative for antibodies to H. pylori, elevated levels of urinary nitrate were associated with increased risk of gastric cancer. The multivariate-adjusted odds ratios for the second and third tertiles of nitrate were 3.27 (95% confidence interval = 0.76-14.04) and 4.82 (95% confidence interval = 1.05-22.17), respectively, compared with the lowest tertile (P for trend = 0.042). There was no statistically significant association between urinary levels of nitrite or N-nitroso compounds and risk of gastric cancer. Urinary NMTCA level was significantly associated with consumption of alcohol and preserved meat and fish food items. Conclusion: The present study demonstrates that exposure to nitrate, a precursor of N-nitroso compounds, may increase the risk of gastric cancer among individuals without a history of H. pylori infection

On the Formation of Vortex Pairs near Orifices

It is pointed out that a two-dimensional vortex pair is commonly generated by pushing fluid down a semiinfinite channel by means of an impulsively started piston. Sheffield (1977) calculated the trajecotories of an ideal vortex pair near channel openings of different shapes. The present investigation is concerned with a point-vortex model of the process of pair formation and a general extension of Sheffield's results. The assumption is made that viscous effects are significant only during the separation process and have negligible influence on the overall flow. In the limit of infinite Reynolds number, the problem becomes one of inviscid flow. The growing vortex sheets shed from the edge are represented by a simplified model reported by Brown and Michael (1954). The model is utilized to study the trajectories of two free vortices released symmetrically near the channel wall far from the opening of a semiinfinite channel when growing secondary vortices are present

A QoS Internet Protocol Scheduler on the IXP1200 Network Platform

In this paper we describe the implementation of a scheduler capable of Quality of Service (QoS) management on the Intel IXP 1200 network processor. First, the scheduling algorithm PTTSD is introduced at the abstract level showing its characteristics and complexity. Then, the IXP architecture is briefly described with the purpose of refining the PTTSD algorithm in order to provide a more efficient implementation. The refined PTTSD scheduler has been implemented on top of the reference design provided by Intel. The dependency of the adopted software architecture on the IXP network processor is analyzed and, finally, the implementation is described A set of characterization tests is reported to demonstrate the efficiency of the implementation and the effectiveness of the Intel architecture to implement flexible QoS routers