Multi-target localization for bistatic MIMO radar in the presence of unknown mutual coupling

A decoupling-estimation signal parameters via rotarional invariance technique（ESPRIT） method is presented for multi-target localization with unknown mutual coupling in bistatic multiple-input multiple-output（MIMO） radar.Two steps are carried out in this method.The decoupling operation between angle and mutual coupling estimates is realized by choosing the auxiliary elements on both sides of the transmit and receive uniform linear arrays（ULAs）.Then the ESPRIT method is resilient against the unknown mutual coupling matrix（MCM） and can be directly utilized to estimate the direction of departure（DOD） and the direction of arrival（DOA）.Moreover,the mutual coupling coefficient is estimated by finding the solution of the linear constrained optimization problem.The proposed method allows an efficient DOD and DOA estimates with automatic pairing.Simulation results are presented to verify the effectiveness of the proposed method.

Meta-analysis of the relationship between cytotoxin-associated gene-A and ischemic stroke subtypes

OBJECTIVE： To assess the role of cytotoxin-associated gene-A （CagA） positive strains of Helicobacter pylori （Hp） in ischemic stroke （IS） subtypes. DATA SOURCES： A computer-based online search of PubMed, EMBASE, the Cochrane Collaboration database, the CNKI database and the VIP database, from January 1997 to July 2010, was performed to find relevant studies. DATA SELECTION： Case-control studies relevant to CagA with IS and IS subtypes were selected. Data regarding related factors in the case group and control group were acquired using the same approach. All patients had been diagnosed as exhibiting IS using skull CT or MRI, and were etiologically typed according to the 1993 TOAST diagnosis criteria. Two investigators independently performed the same search and study selection. Meta-analyses were then performed for the selected studies using RevMan 5.0 software （Cochrane Collaboration） after strict screening. Heterogeneity tests, sensitivity analyses and publication bias assessments were then conducted. MAIN OUTCOME MEASURES： Relationship of CagA with IS and IS subtypes. RESULTS： Eight studies were selected, involving data from 879 patients with IS, and 849 healthy controls. Five out of eight of the selected studies were related to large artery atherosclerosis （461 patients with IS and 497 health controls）. The results of our meta-analysis revealed a significant association between prior infection with CagA-positive strains and increased risk of IS （odds ratio （OR） = 2.31,95% confidence interval （C/）： 1.89-2.82, P 〈 0.01）, In addition, we found an association between infection with CagA-negative strains and IS （OR = 0.57, 95%C1：0.47 0.70, P 〈 0.01）. CagA positive and negative strains were found to correlate with large artery atherosclerosis （CagA-positive strains： OR = 2.87, 95%C/： 2.19-3.77, P 〈 0.01; CagA-negative strains： OR = 0.51, 95%CL 0.39 0.67, P 〈 0.01）. Because of the diversity of etiological factors in the case-control study, we conducted further analyses after correcting for confounding factors, and the overall effects were recalculated. The results revealed significant relationships between CagA-positive strains and IS （OR = 2.36, 95%C1： 1.84-3.02, P 〈 0.01）, and between CagA-positive strains and large artery atherosclerosis （OR = 3.10, 95%C1： 2.29-4.19, P 〈 0.01 ）. A heterogeneity test of CagA-positive strains in IS and its subtypes revealed good homogeneity （f = 0%; f = 0%） and we adopted a fixed-effects model to calculate OR. Sensitivity analysis confirmed that the results of the meta-analysis were reliable. However, the funnel plot suggested that the experimental results may be affected by bias, possibly resulting from a lack of published studies reporting negative outcomes in the meta-analysis. CONCLUSION： Infection with CagA-positive strains is a risk factor for IS, especially the large artery atherosclerosis subtype. However, the evidence from case-control studies is weak, and more prospective studies are required to conclusively determine whether infection by CagA-positive strains should be considered a novel risk factor for IS and its subtypes.

Correlation between Helicobacter pylori infection and atherothrombotic stroke

Previous studies have demonstrated that Helicobacterpylori infection is associated with coronary atherosclerotic heart disease, but the correlation between Helicobacterpylori infection and ischemic stroke remains unclear. The present study assessed the effects of Helicobacter pylori infection on atherothrombotic stroke. This study included 115 individuals with atherothrombotic stroke, all of whom were patients receiving treatment at the Department of Neurology, Aerospace Central Hospital （Aerospace Clinical Medical College Affiliated to Peking University） in China, from March 2006 to July 2009. In addition, 131 controls without the history of cardiovascular disease, cerebrovascular disease or atherothrombosis were also enrolled in the study. Results show that the Helicobacterpylori-lgG positive rate was greater in the atherothrombotic stroke patients than in the controls, but the difference was not statistically significant （67.8% vs. 61.8%, OR = 1.301,95%C/： 0.769-2.203, P = 0.327）. After correction for potential risk factors for Helicobacter pylori infection and known risk factors for ischemic stroke, no significant difference was detected between them （OR = 1.278, 95%C1： 0.667-2.449, P = 0.459）. These results indicate that there is no specific correlation between Helicobacterpylori infection and atherothrombotic stroke. This finding requires further verification in large-sample prospective studies.