Pathways of nitrogen loss and optimized nitrogen management for a rice cropping system in arid irrigation region, northwest China.

The reactive nitrogen (N) loss of the rice cropping system in the arid region shows a different pattern from that of subtropical humid region due to different climate types and crop management. However, little attention has been paid to this region. To fill this knowledge gap, a two-year (2009-2010) field observation was conducted in the Ningxia irrigation region, northwest China, to explore the major pathway of N loss following local farmers' optimal practice. Further, we determined the site-specific emission factors of ammonia and nitrous oxide, rate of surface runoff and subsurface (leaching and seepage) to improve the inventory resolution of arid irrigation region. Results showed that ammonia volatilization (45%-49% of total N loss), leaching and seepage (30%-33% of total N loss) were proved to be the primary factors of N loss in rice paddy fields. The emission factor of ammonia (21%) and N leaching rate (7.5%) following farmers' practice were 2.1 and 5.4 times higher than the country-specific default value in China. The country-specific N runoff rate and emission factor of N2O could be directly adopted in this region. A 20% reduction of N fertilizer to farmers' practice (300 kg N ha-1) alongside the application of organic fertilizer (30% N in synthetic fertilizer was substituted by pig manure) were considered to be the optimal N rate in this region. Our study can narrow the gap between researches on N loss in arid regions and subtropical humid regions. Meanwhile, the results can provide specific advice on N loss mitigation for policy makers in arid irrigation regions.

Study the Diagnosis Value of Transcranial Doppler Ultrasound for Intracranial Artery Stenosis in Patients with Cerebral Infarction / 现代生物医学进展

Objective:To study the diagnosis value of Transcranial Doppler ultrasound for intracranial artery stenosis in patients with cerebral infarction.Methods:A total of 140 patients with acute cerebral infarction,transient ischemic attack and posterior circulation ischemic attack in Department of Neurology,Xinjiang cardiovascular and cerebrovascular disease hospital from October 2014 to October 2016 were selected as research object,CT angiography (CTA) and TCD detection were performed in all patients.Used CTA examination results as the gold standard,the detection results of intracranial artery stenosis in two groups were compared,the diagnostic value of TCD and the diagnostic results of TCD to the degree of bilateral middle cerebral artery (MCA) stenosis were analyzed.Results:CTA diagnosis showed that 140 patients had a total of 105 patients with intracranial artery stenosis,in the anterior and posterior circulation vessel of 1155 intracranial segments,CTA detection showed that 249 vessels were narrow,TCD detection showed that 236 vessels were narrow.Com-pared with CTA,TCD was better in the diagnosis of patients (Kappa value＞0.75).The diagnostic sensitivity and positive predictive value of TCD for MCA were the highest,which were 91.26％ and 93.07％,the consistency was the best (Kappa value =0.917).CTA detection showed that 210 MCA vessels had 103 stenoses,mild stenosis 17,moderate stenosis 41,severe stenosis 45,TCD detection showed that the stenosis was 101,mild stenosis 16,moderate stenosis 40,severe stenosis 45.The Kappa test showed that the diagnostic results of TCD to the degree ofMCA stenosis was better consistency compared with CTA (Kappa value=0.884.Conclusion:TCD has a high diagnostic value for cerebral artery stenosis in patients with cerebral infarction,and it is consistent with the diagnosis of CTA.